Q: How do i load the credit from my apple gift card to my account?

If it's an iTunes gift card, and it was issued in the same country as you and your account are based, then you should be able to redeem it onto your account : http://support.apple.com/kb/HT1574

If it's an Apple Store gift card then it can only be used in Apple stores and the Apple online store, it can't be used in the iTunes or related stores (app store, Mac app store, ibookstore)

Apple and iTunes gift cards : http://store.apple.com/us/browse/home/giftcards