Go to your safe house (police station/night club) and take the teleporter to the Watch Tower/Hall of Doom. From there go to the Meta or Magic wing and there will be a teleporter to Metropolis. If you want to get back to Gotham, the teleporter is in the tech wing.
I never said I wouldn't to lie I never that what I said was true.
If you are 8 then you just got the ability to do quests from other mentors. I'd go now and knock out Batman's missions. I believe Bane is the one that opens up for you. Then I work back and forth between the cities doing the lowest level quests in my journal first.
My power is discombobulatingly devastating. I could feel his muscle tissues collapse under my force. It's ludicrous these mortals even attempt to enter my realm