Categories Need to Stack

In the home page categories section where I add sub-categories it keeps adding more space in the other categories that do not have as many sub-categories. It is like they are all on a box-templet not allowing them to stack above each other. Please see attached pic..

I would like them to stack them like Craigslist or KSL below. What do I need to put in the custom CSS to accomplish this? Thank you 🙂

My site is…. https://saltlakecountyclassifieds.com

I would like them to stack like… https://www.ksl.com/?nid=13