To change any of your account details, log in here.
Then click on 'My account' at the top right hand side of the screen.
Under 'My Profile' you can change your password, address and other information, and your notification settings.
Under 'My Library' you can read, download, buy gift vouchers for or remove eBooks.
(If you have purchased Practising the Piano eBooks, you can log in and change your account details for your Informance account as described above here.)