To register your pre-order code and get early access, follow these steps:

IF YOU ARE FROM NA AND HAS AN NA ACCOUNT: go here
NA pre-order registration[preorder.na.finalfantasyxiv.com]

IF YOU ARE FROM EU AND HAS AN EU ACCOUNT: go here
EU pre-order registration[preorder.eu.finalfantasyxiv.com]

• It will ask you to choose your language
  
• Then log into your account. Use the account that you had when you played open beta or your regular square enix account.
  
• If you are PS3 player, choose PS3, if you are PC, choose PC.
  
• Enter your code it's should be alphanumeric in this format XXXXXX-xxx-XXXXXX-xxx or 6-3-6-3 (as in 6 letters, 3 numbers, 6 letters, 3 numbers iirc) MAKE SURE THAT YOU DONT GET O and 0 MIXED UP. This is the code you got after pre-ordering from Amazon, greenman, gamestop etc.
  
• If you did not get all check marks after each entry field then you made a typo.
  
• If you get error 1 or 3, just keep trying. Log out, log in, try again. Wait later and try again. The page is probably congested b/c too many ppl trying.
  
• Tips for getting it to work: Clear browser cache, refresh page F5 or Ctrl + F5 on chrome. Try it in another browser.
  
• If it worked, you should get a 20 digit serial or a 12 digit for PS3 (99% sure) . This is your early access key and I believe the PS3 key is for you to download it on your PS3 dashboard. Also PS3 players will get a separate instructions on how to use their code. For more go here PS3 instructions.[i.imgur.com].
  
• You don't really need to wait for an email confirmation but one should come to remind you of the code that you got.
  
• They will give you the link to apply this early access key to your account (yea ♥♥♥♥♥♥♥ confusing right? bear with me). If you can't find the link, here it is: Early access key redemption[secure.square-enix.com]
  
• Log in to your SE account again. Make sure everything is right and it is the right account that you intend to play FF14 with and redeem. Now you're good to go