To change the email address linked to your account go to your account, found here.
Hover over your name in the top right corner and click Settings.
You will then be presented with the details you have linked to your account.
Change the email address in the field at the top and then click save at the bottom.
You will then be sent a confirmation email to the new email address you provided.
Once you have confirmed this using the link in the email, you will have successfully changed the email address linked to your account.