As a result, to play the game you do indeed need to pay a monthly subscription fee to Square Enix – generally $12.95 US a month, although the first month is free. You also need a credit card or debit card with a Visa or Mastercard logo for payment of the the monthly fees.
P.S. I assume the version of FFXI you’ve purchased is a second-hand copy of the PS2 version, in which case it is actually unusable. The content ID codes that come with the game are locked to the user’s credit card when you sign up for a FFXI account with PlayOnline, and cannot be reused. This means you can’t resell the game to someone else at a later date. And, if the previous owner has already used the codes and created a FFXI account, then you’ve wasted money on a game that is completely useless I’m sorry to say.
If you still want to play FFXI though and don’t mind paying the fees, then you’ll need to buy another, new, copy of the game in order to subscribe to PlayOnline and play FFXI. The PS2 version incidentally is no longer produced and is regarded as obsolete by Square Enix. There is also the PC version (now released as the Vana’diel Collection with all three expansions on one DVD-ROM), and the new X-box 360 version, which replaces the PS2 version. Either of these two versions are recommended, depending on whether you have a PC capable of running FFXI or own an X-box 360, of course.