How do you turn into a Vilian on LEGO Batman

You have to complete Chapter 1 in Lego Batman. Then you can pull the switch on the 1st floor of Batman's hideout. Batman and Robin will become two villians and will be transported to the Arkham Aslyum, where there are tons of villians to become. You can also do levels from the villian's side, so you will play levels as a villian. To go back to Batman's hideout just pull the switch, and you will turn back into Batman and Robin. After you complete chapter 1 you can visit the Arkham Aslyum any time. Hope this helps!