Adding sub menu links:
If you would like to add an item to the menu in one of the submenus, first, open the menu.js in Notepad or any plain text editor. Check the visual link below. You will find the code shown about halfway down the menu.js.
Adding top level buttons:
If you would like to add a new top level menu item, or "button" on the menu, open the menu.js in Notepad or any plain text editor. Check the visual link below.
The top level menu and buttons can each have their own widths. You can make each top level button different if you would like. See the visual below.
There are many options included with the menus. You will edit the menu.js for most of them. There are also some less common options in the corporatestyle.css file near the very bottom of the file.