To change your email address in your Apple account, this will need to be done through the Apple store since we don't have access to Apple store accounts. (This is how all apps work).

Here's a helpful article from Apple on how to do that: https://support.apple.com/en-us/HT202667

Note: We are better able to help you when you sign up through our website, so if you were prefer to switch your membership to our website, then you can cancel your Apple subscription and instead sign up on our website right here