Once you're logged into your account, click on "My Account" in the grey bar on the homepage. Click on "Action" next to one of your addresses, and then click "Edit" from the dropdown. This will take you to a screen where you can update all of your contact information. Please note that you will need to save changes on two screens (the second one is after you see the green text "contact address updated successfully") in order for the changes to take effect.