...
On the forum, click on your profile image, then click on the grey person icon, (this will bring up your account menu) then click on “Preferences”.
...
This will bring you to your Account Preferences where you can change or amend any part of your profile and account information.
Click on the wrench in the red circle and you will be able to change the email address your account is registered to.
You can also click on + Add Alternate Email,and this will allow you to add another email address to your account.
...