Hey Cindy! When you are in a specific forum, but not in the thread itself (for instance, you are in "Ask the Experienced" and can see all the threads listed), go over to the right hand column. There you will find a little icon that looks like a sheet of paper, a pencil, and an envelope. If you hover over it, it will say "Subscribe to this topic". Just click on that and you are set!
ETA: Ok, maybe not! I can see them in this forum, Ask an Admin, but not in ATE. I'll get back to you.