To update your account email address, simply log in to your account and click into 'My Account' which can be found in the top horizontal menu:
Then in the email field, enter your new account email address and click 'Save Changes':
NB: A re-activation email will now be sent to your new email address. You must click on the link provided to reactivate your account. If your website has been published it will remain live on the internet, but you will not be able to log back in to your account to make any updates until you have reactivated the new email.