How do I change my payment method for an itunes download to my Apple account?

I purchased a gift card and added it to my Apple account. I am trying to purchase and download music to my music playlist (I have about 20 songs that I have previously purchased that are on the list) but the only option that I have that populates the choice list to pay is through Pay Pal. My Apple account shows that I have a balance of $25 but won't complete the purchase using my Apple account. Help!