When you make a menu item, you choose a category to link to, and all child categories/ images within that category will show.
If you want to show all the top level categories, you need to make a category that is a parent of all your top level categories, and then link to that top most category.
For example, to make this page I would use the set up below. In this set up, all the categories have ‘Component Demo’ as their parent.
