This expansion content available on Steam may only be registered and added on a Square Enix account that has the base game “FINAL FANTASY XIV: A Realm Reborn” purchased on Steam.
To view your registration codes after purchase, simply right-click on “FINAL FANTASY XIV” in your Steam “Library” and select “View CD key” on the Steam client. The codes will always be accessible from this location should you ever need to reference them again.
The pre-order code (prefix “RF3A”) that grants early access and in-game items can be redeemed immediately on the Mog Station http://sqex.to/Msp by selecting the “Enter Pre-order Bonus Code (Early Access Code)” option. The in-game items referenced above will be sent to characters on your account at the official launch of Stormblood. The FINAL FANTASY XIV: Stormblood registration code (“RE3A” codes for standard edition and “RG3A” for collector’s edition) can only be redeemed on Mog Station beginning on June 20, 2017.