About cards and codes. iTunes Store Gift Cards: 1  When you redeem an iTunes Store Gift Card, the amount of credit on the card is added to your iTunes Store account. 2  You can use it at any time to buy items in the iTunes Store, App Store, or iBooks Store, pay for in-app subscriptions, or make in-app purchases. Tap You can also enter your code manually.. 2  In some countries, you can redeem gift cards using your built-in camera. 3  If you have an iTunes Store Gift Card, enter the 16-digit code, which starts with X, from the back of the card. 4  If you have a promo or content code, enter the code from the back of the card. 5  Tap Redeem.