Hiding subforums from main page

Hi, I want to put a bunch of subforums to organize my forum, but having them all on the front page keeps it cluttered and defeats the purpose. I am using PHPbb3.

I have a category with 7 forums.
One of these forums I want to have 3 subforums.
In each of these 3 subforums, I want to have additional subforums.

I only want the subforums of each forum to display when viewing the particular forum.

For example, I want to have the one forum visible from the front page. After clicking on this forum, the 3 subforums inside would become visible, but the subforums within the subforums would not be visible. After clicking on one of these subforums, the additional subforums would appear.

Where is the setting for this?

Go to Admin CP > Display > Structure & Hierarchy...
Split categories on index : Select "Medium"
Click "Save"