To change the registered email address:
Go to your User Profile > Account
Click on the "Change" button located next to your email address
Enter the new email address you wish to use in the designated "New Email Address" field, and click on "Verify New Email" button to proceed.
Please note that each time you change the registered email address, the new email address will have to be verified.
The ability to change email address depends on the registration method and is not available for the accounts registered via Google.