How do I use the apple gift cards in passbook for a purchase in the apple online store.

Apple Gift Card

http://www.apple.com/gift-cards/

You cannot use iTunes gift cards to purchase at the Apple Online Store.

If you have got iTunes gift cards, you can use them to purchase content in the iTunes Store, App Store, Mac App Store and iBookstore. If you have got Apple Store gift cards, you can use them to purchase things at any Apple Retail Store or Online Store

Hi Ron2002,

Click this link and redeem your Apple Store Gift Card:

http://store.apple.com/us/browse/home/giftcards/redeem

Be sure to sign to your Apple ID.

Cheers!