To change your email address, you need to be logged in to your account area. Once you are logged in, select the 'My account' link from your Dashboard.
Then simply update your email address, and save your changes. Be especially careful to type your new email address in correctly because if you make a mistake, your next attempt at logging into the site will fail (unless you can remember what your spelling mistake was) and no one will be able to contact you. If you want to test whether you have successfully changed your email address, set up a new email alert. You should instantly receive an auto-email at your new address confirming that you have created a new alert.