When you make a reply, if you use the full reply mode and expand the 'Attachments and other options' block just below the text box, there's a 'Notify me of replies.' option.
There might be something else that's easier in the forum account settings... like the following I just found at 'forum profile' -> 'modify profile' -> 'notifications' and the 'Turn notification on when you post or reply to a topic.' option.
I'm still getting to know the forum software myself so there might be an even easier way than either of those options.
-dro
