You gotta be loving kidding...
Enable them on your add-ons list, start a game, go to options and map the JVS actions that will apear under controls to different keys, set your wrench to JVS mode and use it on the brick you want the door to be under, slecet the king of door, give it a name, set any additonal features (Such as an admin only door or a minigame only door) and go nuts.