How to add top drop-down menus?

[tkmops]

How does one add the top drop-down menus 'Categories', 'Products', and 'About Us' to my site so it looks like this.... http://themes.withinpixels.com/autumn/?

I've already gone to 'Modules', and 'top horizontal menu'...but this is for 'Add a new horizontal menu to the top of your e-commerce website'. Doesn't my autumn theme already come with 'Categories', 'Products', and 'About Us' drop-down menus already built in? I've created 4 categories and added them from the left pane to the right pane, and saved, but the drop-down menu 'Categories' is not showing up. Anyone know how to build a 'Categories' drop-down menu so it shows all my categories? Thanks!