You can edit your site's navigation menu(s) through the admin backend. To begin, click on the Admin Backend option under Quick Links.

Scroll down and select the Navs module from the list of available modules.

Click on the navigation you'd like to edit. Keep in mind that some sites may have more than one.

After selecting the navigation you wish to edit, you'll be taken to the edit screen. Make the desired changes and be sure to click save before leaving the page.