Quote Originally Posted by Dogempire View Post
I already redeemed it, the game gave me a white devil identification key.

I don't really know how to use it.
OOOOH
Oh okay I understand now...sorry X)
When you reach, I think, Main Story Quest level 20, you'll be able to rent/own a chocobo, which is your first mount (it's when you choose a Grand Company to ally with). That's when you can start using mounts. When that's available, just "Use" the identification key and the mount will be put into your mounts you can choose from.