it's really easy, but for those of you who don't know how:
1. go in you're v12 folder and launch the dedicated.command. the game should start automatically.
2. if you have RTB, when you are promted in consle to, type this in console.
setupRTBDedicated("YourUsername",1);
(youreusername is replaced with your screen name, witch you have to do)
if you don't have RTB, skip step 2.
3. launch an internet game.
You're done!
(note: for some reason, the dedi will shut down if you turn you computer off.
hosting a dedicated LAN game:
same thing, only you run the dedicatedLAN.command instead and launch a LAN game.