External Links in Navigation
To create an external link menu item, select the desired folder (or the Base Folder for a menu link at the top level of the site) by hovering over the asset under the Site Content menu and clicking on the arrow to the right of the asset name. Select External Link from the Add Content menu.
Appropriate information should be entered in the System Name, Display Name and Title fields of the Content tab. Display Names and Titles show up as the menu item and the web browser window or tab title (respectively) just as they do with pages.
Once all three names have been entered for the object, Save and Submit changes.