Hello Veronique,
You can actually choose either Email Adderss, Regitration Confirmation Number or Cvent ID.
You can see if you are using Email Address or Cvent ID by going to
Website & Regitration > Registration Settings > click on the registration path in question (if you have only one path it will automatically go into the path) > click on the
Identification & Security tabUnder the Registration Indentification header you will see how Cvent is setup to identify registrants:
- Email Address
- Source ID (Cvent ID)
- Email Address and Source ID
You can run a Contact Report to show the Source ID / Email Address so you can upload the attendees to the Session in question.
I hope this helps.