Well, as they created a forum account today - that is a frontier account, so they can link it to that. Or create yet another, but only security paranoids like me would do thatSo, have you actually created a frontier account for the game to link to?
It's Have Only Link Account It didn't have a create new account tho
So from that "box / window" you follow the sequence shown here:
Creating a Frontier account after purchasing Elite Dangerous on Steam.
When you first start the game from Steam the launcher will pop up with this message as shown below: Click 'Create New Account' and you will be brought to a page where you will need to enter you...support.frontier.co.uk