Feel free to use onee of the codes.

B8HDG6ST
C7TJTXUG
RNKPDWHT
VYCATRKV

1 - Create a Square Enix account.
2 - Log into the Mog Station.
3 - Enter the game code you got when you bought the game.
4 - Click on "Manage Service Options"
5 - Click the button that says "Enter Recruitment Code"
6 - Enjoy the game!