Anyone can create a game. The character sheets only exist inside a game instance, so you would need to select the character sheet you want to use when you create the game. Then, when you join a game, you might be able to move the character you want to use from your game to the Character Vault (accessed under the big Tools heading at the top of this page). I say "might" because a lot of people running a game will have certain custom rules of character generation or maybe would want to be involved in character generations, so may not even accept pre-built characters.
