First, some terminology. In Simplweb, the word menu has a variety of meanings, none of which should be confused with a food menu, like you see at a restaurant!
Each of the buttons on your site's menu is much, much more than a button. In Simplweb, these buttons are called menu items. Each menu item is also called a menu link because when you click on a menu item, you are taken somewhere else in your website.
Menu items are grouped together in a menu that has its own unique name. The major navigation menu on your site, the one that displays across the top from left to right, is called, not surprisingly, mainmenu. Each menu has a Menu Item Manager associated with it.
You can see the various items in the mainmenu group by placing your cursor on the Menus choice along the top of your backend screen and waiting a second. A drop down menu will appear. Move your cursor down the list to the words Main Menu* This screenshot shows your where to find this option: