It technically starts at 6:00 PM, but most people show up after 6:30 PM to 7:00 PM. At any case it lasts until midnight. If you're showing up, it's recommended you bring a setup, since more setups = more fun~
Ah it's all one building, so it's not too hard to find your way around. The room name is Van Gogh, which is towards the end of the hall on the left if you take the first right (not the staircase) after you enter from the front.