Great question Scrambler,
I'm not a moderator nor am I even close to an an expert on the forum software platform, but I think if you click on the username to the left of the screen (for instance, clicking on my username of this message) you should see a pop-up that allows you to "Follow", "Ignore", or "Start Conversation".
Follow is I think the same as "friending".
"Starting Conversation" is the PM system, as far as I'm aware.
I hope that's helpful!