Assuming that you pre-ordered from the SE Store, these are the steps you will go through.
1) Pre-order the game on the SE Store. Your credit card won't be billed at this point.
2) They send you a
pre-order code.
3) Go to
https://redeem.finalfantasyxiv.com/na and log in using your MogStation account. Register the pre-order code and choose the appropriate platform. You will unlock your pre-order bonuses.
4) The website will then give you an
Early Access code.
5) Register the Early Access code on the MogStation to unlock Early Access. You will now unlock Early Access.
This is the final step you can do before the official release day.
6) When the game is officially released, your credit card will be billed.
7)
On 20th June, you will then get the
Stormblood game code. Register the code on the MogStation to officially get the full expansion on your account.
I hope this clears everything up. You will get 3 codes in total. Pre-order code, Early Access code and finally the Stormblood code itself.
Additionally, you can force the SE store to bill your credit card right away instead of waiting for the Official Release. Just log on to your SE Store account and under your orders, there will be an option to "bill right now". You will be billed right away but you will still only get the full Stormblood code on the official release day.