Navigation menus are automatically generated based on the sections in your branch.
If your site structure looks like this:
Your navigation menu will look like this:
Black folders will show in the navigation
White folders won't show in the navigation
Because navigation menus are made from the site structure, you can change your navigation menu by altering your site structure.
New items are added to your menu by creating a new section.
Change the order in which sections appear in your navigation menu and in the site structure.
How to make a section (page) not appear in your navigation menu.
How to create navigation sub-menu items.
How to add a link to your navigation menu to a section that is not in your site structure.
How to move a section to a different parent section.