How To Create Sub Categories, Listings Directory App

Creating sub categories in the Listings Directory app is very much creating sub pages for the rest of your website.  On the Add/Edit Page, you just select the Parent Page from the drop down menu, of the category you want this category to be under:

Simple, right?!  Now this new page will be under that Parent Page.

If you want a Sub Category to display under a Category in the Listings Directory display, just make sure that display is checkmarked: