Hi there,
if you go to:
https://generate.support/wp-login.php?action=register
Then in the form provided you will:
1. add username you would like to use in the new forum
2. add the email address you want to use in the new forum
As a GP Premium user click the GeneratePress – > Get Support Key button. A pop up modal window will open and if necessary ask you to login to your GP Premium account. Which will then return the support key.
If you also own GB Pro you can repeat that step, or move on.
Once thats done you can do the T&Cs check box and click Register.
let us know how you get on, or where it fails