New User (No user ID yet)
From Menu -> Account, you tap Not registered yet? Sign up here (1) at the top of the account screen, and enter a User ID (2), e-mail address (3), and the country for Amazon marketplace pricing (4). After tapping the Register (5), you will receive a confirmation email with instructions on activating the service. Please follow that email carefully. Video is here.
Existing User (Already has user ID)
From Menu -> Account, you enter your existing user ID (1), password (2), email (3) and country (4) in the account screen. If you forget your user ID or password, you can click here to retrieve. You can also check your account status by tapping Check (6). Video is here.