The QR code comes embedded in the badge that you need to generate for your attendees using the Badge builder tool.
You can also go to each attendee's detail page to print their respective badges.
Your attendees will wear this badge and using the scanner, the exhibitors can scan the QR code embedded on those badges. Attendees can also do the badge scanning to collect each other's contact information.
All these data collected are saved under vCards & Meetings tab in attendee dashboard and also in the backend.