Go to your account Summary, and click Manage emails to add a new email address. After you verify the new email address, go back to your account Summary and select to use the new email address for logging in. You can remove the old email address.
When you sign up for SPiD, you need to accept the SPiD terms and conditions. To use your SPiD account to log in to participating sites and services, you also need to accept the terms and conditions the first time you log into those sites and services.