Here's how to use a Yahoo! Store gift certificate:
Go to the Yahoo! Store associated with your code.
When you get to the Yahoo! Store that your gift certificate came from, you can browse or search for items you'd like to buy.
Once you've added your items to your shopping cart, click the "Checkout" button.
Locate the "Coupon Code / Promotional Code" field. Make sure that you enter the complete gift certificate code. It must start with the "@" sign. Click the "Apply" button to see the gift certificate applied to your order.
If you have more than one gift certificate for a particular store, you may enter and apply these codes one at a time.
If you have enough funds on the gift certificate to cover the cost of your order you won't be required to enter any payment information.
If you don't have enough funds on your gift certificate to cover your entire order, you will be required to pay the remaining balance.