If you have pre-printed QR codes, you will need to activate them and pair them with a unique person. Keep on reading to find out how you do this:
Within the event, click on 'Mission control'.
Go to 'Settings'.
At 'General settings', tick the box to 'Enable Custom ID connection'.
When that's settled, the next step is to find the person you want to connect the QR code to.
Go to 'Crowd check-in'
Search for the person through the search bar.
Click on their name.
Scan the person's ticket.
Now it's time to connect the person to the QR code. Click on the link icon at the top right side. It's next to the print icon. Then, scan the QR code.
The QR code is now connected to the person.