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In order to purchase and download eBooks, the Kindle must be registered to your Amazon account. If you do not have an Amazon account, create one before continuing.  Press the "Home" button. Press the "Menu" button, ensuring that Whispernet or wireless internet is turned on. Select "Settings". Select "Register" from the "Settings" screen. Sometimes "Register" will exist within the My Account submenu.  Enter your user name and password (the e-mail address and password associated with your Amazon account). In order to purchase eBooks on your Kindle, you need to choose a valid payment method on the Amazon.com website. This can be a credit card, debit card, or Amazon gift card.  Visit "Manage Your Kindle". Click "Kindle Payment Settings" on the left side of the page. Click on "Edit" to update your payment method, then follow the onscreen instructions to choose or add a payment method. Click the "Continue" button to confirm your payment method. The Kindle Store is where you will purchase and download eBooks for your Kindle.  If you have a Kindle Fire, select "Books" or "Newsstand", then select "Store". If you have a Kindle Paperwhite, select the "Shop" icon. If you have a basic Kindle, press the "Menu" button, then select "Shop in the Kindle Store". When you have decided on a title or a periodical, select "Buy"or "Subscribe now". Once the content has finished downloading, it will be available on your "Home" page and through the "Kindle Library" or "Archived Items" sections within your device.

Summary:
Register your Kindle device. Set your Kindle's payment method. Navigate to the Kindle Store. Purchase eBooks or subscribe to periodicals. Access your new content.