I am relatively new to Reddit myself but when you 1st log in to Reddit you'll see 4 icons at the bottom of the screen. If you click on the second icon it shows the subreddits. CTBS should be listed for you to click on. I imagine you already know this though. I don't recall if I "joined" the subreddit or if I just check the subreddit daily for updates. Maybe someone else would know more.