New to PH2020 --- Subtopics in TOC?

I'm coming back to RoboHelp after a long absence (RH11 was the last version I used), and I'm trying to wrap my head around all the new features.

I'm getting the hang of it for the most part, but I'm a little confused about how to handle subtopics in the TOC.

Basically, what I am working on is a manual with about 1000 topics.  There are 8 main sections to the manual, each section having between 4 and 8 chapters.  And each chapter will need to have at least 2 heading levels (Heading 1 and Heading 2).

Also, we want the manuals to be output to web and PDF.

I have all of the topics imported and ready to add cross-refs and fix up the bullet and numbered lists, but I'd like to get them all in the TOC properly. Can someone point me to a tutorial or a post that would explain the process of how to arrange my TOC properly?  

Thanks in advance!