1) Under Settings tab, click on Account Info.
2) Scroll to Account Details and click on Edit.
3) After clicking edit, you would be brought to a new page. Enter your new admin/notification email in the "Notification email" field.
Do note that you will have to enter your existing password or a new password in the "New password" and "Confirm new password" field.
4) Click Save and you have updated your admin email address.