How to Add an Amazon Card to a Kindle Fireby Aaron Parson
Any Amazon gift card, whether branded as a Kindle gift card or not, can pay for books, apps and other media for your Kindle Fire. To use your card's credit, you can enter the card number directly on the Kindle or type it in on Amazon's website. Redeeming a card ties the funds to your Amazon account, so make sure you log in with the email address used to set up your Kindle.
Redeem on Kindle
You can add an Amazon card directly to your Kindle Fire through the Settings menu. Swipe down from the top of the screen and tap "More." Press "Applications," "Appstore" and then "Gift Card." Key in the redemption code on the card and tap "Redeem." This process works even if you don't plan to purchase apps with the card.
Redeem Via Website
Amazon store credit carries over between the website and your Kindle, as long as you're using the same account on both. On your computer, click "Your Account" on Amazon's top menu bar and then click "Apply a Gift Card to Your Account." After you enter the number, you can shop for Kindle purchases either on the website or on the device itself.