In the demo version Top menu is located here:

To add or change a Top Menu, go to the Appearance → Menus

Then you can select a menu to edit or create a new menu:

If the Top menu you need is not in the list, just create a new one:

Then tie the new menu to the top menu area:

Then you can add menu items. More details about this you can read here: https://en.support.wordpress.com/menus/