You can create your main navigation in Appearance->Menus. You will see there a lot of new option for every menu item and you can also show HTML blocks for item dropdown.
You can find the instruction in our documentation here http://xtemos.com/documentation/?theme=basel (see “Create menu”).
Write us if you will have any difficulties.
And we would be more than happy if you will rate our theme with 5 stars on themeforest in case you like our theme and are satisfied with our support service 🙂