How to Manage Your Kindle Fire HD's Amazon Account
You buy things from Amazon by using the account and payment information you provide when you create an Amazon account. You probably have an account if you ever bought anything on Amazon (or opened an account when you bought your Kindle Fire HD).
To buy things on Amazon with your Kindle Fire HD, you need to have associated your Amazon account with your Kindle Fire HD, which happens during the setup process, or which you can do by visiting the My Account section of Settings.
Swipe down on the top of your screen, tap More, and then choose My Account in the Settings page to view this screen.
After you associate your device with an Amazon account, you can manage account settings by following these steps:
Navigate to the Amazon website by using the browser on either your Kindle Fire HD or computer.
Tap (if you’re using a touchscreen device) or click the Your Account option in the top-right corner of the Amazon screen.
Tap or click the Manage Payment Options or Add a Credit or Debit Card option from the Payment section of your account.
Change or enter a new method of payment and billing address.