In order to activate the Amazon gift card you have to first sign into the Amazon accounts. If you don't possess an account yet, then need to sign up for one. After you log in, go to the gift card option, and then click the "Redeem the gift card" button. After that, you can simply enter the claim code that you have to redeem your gift card and you're done.
Amazon.com/redeem | Amazon redeem | Amazon.com/mytv