I use to play here years ago and recently came across it again. However, I have since forgotten much of how things work on the site.
I have posted a few games in the waiting room and began playing a couple, but how can I join a game someone else has posted in there? thanks for any assist with this.

I think you can't, it's done automatically by the system. You can send an invitation to a specific user to play an unrated game.

ok ty