How do I host a custom game?
Change your Game Mode to Arcade by clicking on the blue "Change" button. Hit the "Play" button and you'll be taken to a page with the list of open servers to join. You can either join any of the games listed here or you can host your own custom game by clicking "Host New Game" or pressing the 'N' key. Alternatively, you can navigate to the Arcade Games tab in the upper left to host a custom Arcade game.