You will need to Claim a gift certificate that was purchased through the checkout proccess by yourself or another person before you can use it. An e-mail with the gift certificate code and amount will be sent to the person who purchases the gift certificate. You can do one of two things to redeem the gift certificate.
1) Simply login to your account page and enter your code into the "Claim Gift Certificate" field.
2)Save this code and enter it in the "Claim Gift Certificate" field in your Shopping Cart as you are checking out.