Joining a Game:

to create or join a multiplayer room, select vs play, and choose a lobby (coordinate with your friends, etc)

to join a new room, click the room in the list, and hit the join room button, if you want to CREATE a room, hit that and you'll be presented with this:

fill in as you see fit.

GAME TYPES:
- the default (as shown above) is free-for-all, everyone against everyone else, for lowest score.
- the other option is team play, which is may be 2x2 playing off of each other's shots. (aka, you go, your teammate goes, you go, etc. using the same ball)

(thanks to kitch and forseti for pointing this out)

after that, you'll be in your own lobby:

select the course (left/right selects course, down and up selects the front nine, back nine, random, etc.) - be stingy with the starred ball. it earns you more money, but it doesn't last forever and the only way to get another is to pay real cash for one.