Two options:
OPTION 1: If you still have certificates in the old system, please join via the link provided in the email to active your member account (as it makes a link between the old and new system).
Your certificates will be migrated to the new system early March, using your email address as the 'unique' key between the old and new system.
OPTION 2: If you do not have certificates in the old system, just create a new member account using your new email address.