The email address that you use to login with is the same one that you will receive our emails to. If you want to change it, please login to your account and choose 'Profile'. You can also hover over your name and then choose 'Settings'.
Then choose 'Change email' in the left-hand menu. You'll be taken to a screen where you can enter your new email address. Then click the blue change email button.
You'll receive an email to the new email address that looks like this. Click the "Confirm your email address" link.
You have now successfully changed your email address! Use this from now as your username to login with.