Today, Apple released an update for their Apple Store iOS app which includes support for making purchases with a gift card. This feature wasn’t present in the last update, leaving angry people who just got a gift card for their birthday and had no way of spending it though Apple’s Store app. The only way to pay through the Apple store app previously was with a credit or debit card.
You can either scan you gift card on the Store app with your iPhone’s camera or import the gift card from Passbook. Then the gift card balance is added to the order balance.
You can download the Apple Store app right from here.