Display Subcategories on Category Page

Hi, I have a question.. I am trying to figure out why when I add a subcategory to a category it shows up as a new page on the main page.. any way to have it show up like..

Category
-Sub Category

? Here is the site link, https://www.dakidezain.com/CircleCity

I tried to find the solution for the past 2 days and found some codes but everything I tried hasnt worked.. and on the Appearance-Widgets of this theme it says

No Sidebars Defined

The theme you are currently using isn’t widget-aware, meaning that it has no sidebars that you are able to change. For information on making your theme widget-aware, please follow these instructions.

can anyone help me? ill even pay if I have to just to get this fixed! thanks!

email is: [email protected]