Show Subcategories in Category sidebar

I’m using the template “Icon Focused” in the “Category Focused” category of templates. In the view for a single article, there is a sidebar on the left showing the main parent Categories and the number of total articles within each, but does not show how they are split among any Subcategories. I’d like to edit the code that creates that sidebar to show subcategories and how many articles there are in each (rather than the total in the main category). How can i do this? Thanks very much!