The listing, Gotham City Impostors: Premium Card Pack 2 [Steam] has ended.
It's a steam redeemable key. You need a steam account to activate it.
http://store.steampowered.com/app/216457
I will send the key to the winner via PM.
Activating a Product on Steam
How do I register a CD Key to activate a product on Steam?
1.Launch Steam and log into your Steam account.
2.Click the Games Menu.
3.Choose Activate a Product on Steam...
4.Follow the onscreen instructions to complete the process.