Unlinking a menu item is straightforward. 

To do this:

1. Click "Admin"
2. Click "Menus" on the left
3. Select the folder where the menu item is located
4. Under "Manage current menu" click the trash can icon next to the item you wish to remove, then confirm your selection by clicking "Okay"

Now preview the site by clicking the globe iconin the top righthand corner of Site Builder. The menu item should be gone.

A few notes: 

• Unlinking a menu item only removes the navigation to the page, not the page itself. (The page is still retrievable through bookmarks, search engines, or typing the URL directly into the address bar.) If you need to remove a published page, be sure to delete the page.
• You can add a main navigation menu item or submenu item back to the navigation after it has been removed.