sub category inside product page only

[pixel9studio]

Hello All,
I am super new to prestashop, and have a question... I have a horizontal menu, that I want only to show the main categories... when you press it, it goes to a "subcategory page" with thumbnails ...
for example: main menu button: apparel
then, you click on it, and instead of showing all the apparel image previews, i want to have:
boys and girls
then when you click on one of them, you go to the product page... with the ability to have the subcategories on the side of the screen...
how can i do that?

thanks so much.