How the hell do you join/start a game?

Thus spake favedave:

OK, I realize this is open source and all, but where are the
instructions on actually joining a game? Certainly not in the wiki.

The instructions are in the User’s Guide. Look in the Help menu.

I downloaded the Acquire module, saw that there was another player in
the lobby under the Acquire folder, but no amount of clicking or
anything would do anything like “join” or “start” or anything like that.

If the only other user is in the lobby, then there is no game to join.
Someone needs to start a game first. You do that by creating a room.