There are a couple of pieces to this puzzle. You need an Amazon S3 Account and a tool to upload and manage your Amazon S3 files.
Signing up for an Amazon S3 account is a very simple process and only takes a minute. Go to http://aws.amazon.com/s3/ and click on the Sign-Up for Amazon S3 button. If you have an Amazon account, you can use it as your Amazon S3 account.
You will need to provide a payment method and agree to the rates and terms of service. After you receive a confirmation email that your service has been setup, you are ready to go.