Sub-Categories Not Displying Like Categories

I have created sub-categories for my main ones, but when displayed, they are one after the other. For examples, the main category is Coupons and has 3 sub-Categories: Home, Garden, Toys.
It displays like this:

Coupons
Home Garden Toys

and I want it to be displayed like this:
Coupons
Home
Garden
Toys

(basically the way ALL primary categories are displayed).
I need a break (<br />) or new line between the sub-categories, but don’t know where to insert it.

Please help. Thanks you.