How to change horizontal sort to vertical

[Jar3300]

Folks,

I'm fairly new to Prestashop. I putting together a store for a friend. She has no subcategories and 64 categories. I tried to get her to organize it in a more condensed fashion, but she wouldn't have it. The top horizontal menu sorts the categories horizontally instead of vertically. How can I change that?

This is where it is. 

 

Thanks in advance,

Jim