To link a programme to your marketplace user go to the User Dashboard and open the tab Link or Manage Accounts. You will be taken to the Manage Accounts page where you can add a new programme. Simply enter the user name and password you used before to log in to the programme in the zanox "classic" User Interface and click Add Account.
NOTE: You can only link a programme to your marketplace user if you are the owner of that programme. To join a programme you are not the owner of you must be invited by the programme owner or admin.