Go to the website, and click the "create game" button. Set the players and special limits to your liking (I just use the default, which is ten). Set the point limit to your liking (I always use twelve). Select the timer to unlimited, so that players don't get kicked for taking to long. Add whatever decks you want (I normally use the third edition).
To add the Cosmere cards, type /addcardcast TUTKH and /addcardcast QFBZ4 into the chat box.