Board Thread:Game Discussions/@comment-109.152.109.126-20140523124453/@comment-24862049-20140523132443

Once you redeem a gift card the entire value is added to your iTunes account. You do not have to do any else to purchase new items except purchase them. When the remaining balance is not sufficient iTunes will either say you need to add a valid payment method or use a cred card automatically if you have one in the acccount.