The address provided at registration is not modifiable. You can however add delivery and billing addresses from your personal space. To do this, log in, click on "My account" and then "My addresses". Click on the "Add an address" button and fill in your new address using the form. At the bottom of the form you can define whether this address is a Delivery or a Billing address. You can change your address at any time during the delivery step from your cart.