You must redeem your gift card on your account before you can use it with the Amazon 1-Click ordering service. You can also click "Redeem a Gift Card or Promotion Code" on the checkout page to ...

To redeem an Amazon gift card, you can transfer your gift card balance onto your Amazon account so it's ready the next time you want to purchase an item from Amazon.

Gift cards can be redeemed from a device running Android; users will need to access their Amazon account page and type the code printed on the card in the corresponding section.