I am sure there are lots of questions about using Discourse. I invite you to post them on the “Feedback” category on the LLVM Discourse. https://llvm.discourse.group/c/feedback/2
You can also check out the Discourse User Guide here - https://meta.discourse.org/t/discourse-new-user-guide/96331
If you want to get notifications (email or otherwise) on categories and sub-categories, you just click the bell icon as show in the photo below when viewing a category. More details in the user guide that I mentioned above.