Open Account Settings.
Change your email
Enter your current password and the new email address, then submit the change. Follow any activation message sent to the new address.
Change your password
Enter your current password, then enter and confirm the new password. Use a strong password you do not use for another service.
If you cannot remember the current password, sign out and use Forgot password instead.
Worth knowing: Changing your email affects account notifications and future sign-in. Check it carefully before saving.