When editing a page, you have the option to create that page in a menu. In most cases you will want to do this so that it is easy for a visitor to locate that page. When you are creating or editing a page, look for the Menu Settings section in the right sidebar. You can indicate the menu link title and exactly where in the menu the page should be listed.
If you'd like to rearrange links in your menus, the easiest way to go about this is to access the menu system directly. Choose Menu in the black administrative toolbar and you will see a list of menu links on your site. Notice that you can drag the links into any order, and even nest links. It is also possible to remove links from your menu by unchecking the Enabled box, though doing so here doesn't delete the page -- only removes it from the menu. If you’d like to add an external link to your navigation, simply type the name of the link into the “New menu item” field. A new window will appear where you can type the URL of the external link. You should now see the external link icon next to the name of the site in your navigation.