To create an item for a horizontal or sidebar menu, you need to add a Menu Item to an exsitng menu such a Main Menu or create a new menu if you need. 

Menus -> Main Menu -> New

When you are creating Menu Items you are taking two steps at once.  You are creating a link to a web page and you are telling Joomla what type of Content to put on that web page. Joomla will use the Title of the Menu Item as the text for the link in the navigational menu.

The Menu Item Types available are as follows:

Each Menu Item Type will have ways to change the settings to modify its display it the Details tab. Some of these settings are unique for that type, some settings are common to all types. The joom3 focus pages for each Menu Item Type will cover settings unique for that type. Below you will see descriptions for the settings that are common to all types.

The Details Tab

Menu Title: This is what you will see as the link in the navigational menu that can be created with the menu using a Module. This Menu Title will also be used as the alias, unless you type in something different for the alias. Therefore, this Menu Title will be part of the URL for the page.  It can alos show up as the main heading for the page, unless you choose to overwrite it in the Advanced Options with a  Page Heading.

Alias: Joomla will automatically take the Menu Title and make it all lowercase letters, replace spaces with dashes and takes out any symbols.  This is used in the URL for the page in the browser's address bar.

Status: You can set the web page as Published, Unpublished or Trashed.  Unpublished will remove it from the menu on the web pages displaying the menu, but it will still show up in the list of menu items for that menu. Trashed will take it out of the list, but it will stay in the system until you "Empty the Trash".

Link:  This is the PHP created URL for the page. The box is greyed out, meaning that you cannot alter this text.  You may copy it for use elsewhere, such as for links to this page from other places in your site.  Joomla will keep this link as it is, even if you change the title of the page or the alias. Note, it won't have the complete url for the page until you save the Menu Item.  It looks something like this:

index.php?option=com_content&view=article&id=2

Menu Location: You may have several different Menus set up for your site for use on different sections, you may choose what Menu this Menu Item is to be associated here.

Parent Item: You may have multiple levels for your Menu, with sub-items. If you leave it at Menu Item Root, this menu item will be place at the top level.  If you wish this menu item to be sorted under some other menu item, you can select that Parent Item here.  This means that this sub-item may appear in a dropdown list under the Parent Item depending on how you have your menu set up.

Ordering: You can place this menu item in the proper order here, or you can save it and move it around in the list by clicking on the double arrow at the upper left corner.  This will rearrange the items on the list by what order they will show up in the menu.  Clicking on that double arrow also allows you to grab the Menu Item by the three black squares on the left end (a symbol with four arrows will show up) and drag the item to its proper location.

Access: You can set this menu item to only show up for certain Access Levels such as Registered here.  If it is set to Registers, the Menu Item will not show up in the navigational menu unless the visitor logs into the site from the Front End.

Default Page: You can set this page as the default home page for the site.  At least one menu item somewhere must be set as the Default Page and only one Menu Item from all of your Menus can be set as the Home page, so if you say Yes here, which ever page that has the Default setting will be changed to No. You can also change this setting in the list of Menu Items by clicking on the star symbol for that Menu Item.

Target Window: This sets what sort of browser window will open when the visitor clicks on the Menu Item in the navigational menu.

Parent: This means that the web page will open in the same browser tab as the current page, thereby replacing that page.

New Window with Navigation: This will open up the target page in a new browser window or tab - depending on your browser.

New Window without Navigation: This opens the target page in a browser window - but the window will not have the toolbars or the ability for the visitor to enter a new URL.

Template Style: You can set a different template for just this page if you wish.

Language: You can specify a language setting for this page if you have other languages installed on your site.

Note: You can add a note about this page if you need to remember something or for other contributors.

ID: Each time you create a new Menu Item, the database assigns a unique ID for that item.  You cannot change this value.

Common Advanced Options for all Menu Items

Article Options

The Article Options allows you to override the global settings for this set of articles. These settings are covered under Article Manager Options in the Content Section.

Link Type Options

The Link refers to the page name in the menu.

Link Title Attribute: If you want the Link to have a title="" attribute for the <a> tag in HTML, you may enter it here.  What a title attribute does is create a small text box on the screen when the cursor hovers over the text.  You could put a brief explanation in there or possibly a teaser for the article.

Link CSS Style: If for some reason you want to have the link have a certain look to it, you can create the style class in your templates CSS stylesheet and enter the name of the class in this box.

Link Image: This is where you can assign an image for the menu hyperlink. This is optional.

Add Menu Title: If you have the image loaded, this will add the menu title next to the image. If you have an image loaded and set this to No, the image will appear by itself.

Page Display Options

These are settings for the page with the list of Archived Articles.

Browser Page Title: If you want the name of the Browser Page to be something different from the Menu Item name, then you can put that here.  This will replace the Menu Item Name For Example you might want the Menu Item to have a short name for space savings reasons, but have the Browser Page Title to be more explanatory.  The Browser Page Title shows up in the tab of most browsers, though for long names, or sites where the site name comes first, you may not see the Browser Page Title. This Title shows up in its entirety in Search Engine results and at the top of the page in a Safari Browser. 

Show Page Heading: This will either show the Menu Item Title or the Page Heading as entered below.  You may not want to have either of these show because you want the Artilce Title to be at the top of the page.  If so, then leave the setting at No.  

Page Heading:  This is the <h1> text at the top of the page - if you want something different from the Menu Item Title, put it in here.

Page Class: If your template is set up to recognize this feature, you can have a class set to this individual page.  This is a nice feature if you have some styling that will be needed for this page - it allows you to target that page alone.

Metadata Options

Metadata is the information placed in the <meta> tags in the <head> section of your HTML document that instructs the browser what the content is for the web page. You can have global metadata set up for every page on the site, but then taget specific pages with a Meta Description and Meta keywords.  Many SEO experts will tell you that the Meta Description is beneficial in helping Search Engines list your web pages properly.

Meta Description: The information placed in this box will be inserted and the content for the <meta content="" name="description"> tag in the page's <head> section.

Meta Keywords: The information placed in this box will be inserted and the content for the <meta content="" name="keywords"> tag in the page's <head> section.

Robots: This will instructions to Robots (Search Engines such as Google and Bing have robots that crawl every page of your site) whether to index this page and/or follow the links on the page. 

Module Assignment for this Menu Item

This will show a list of alll of the Modules that have been created for your site. Under the Display heading will be a list of boxes that say All, No or Yes

All means that that this Module has be assigned for every page on the site.

No means that this Module has not been assigned for this page

Yes means that this Module has been assigned to this page.

You cannot change these settings here.  You need to go into Extensions -> Module Manager and change it for that particular Module in question.