A QR code is sent to each ticket holder so that you can check the tickets for your events held at the venue at the door. They can access this QR code from the e-mail sent to them. The QR code example is below;

If you scan this QR code with the camera of your phone at the door, you will come to the screen where you can directly access the ticket information (you must be logged into the system with the device you scanned). The ticket you read here will be updated as joined. Here you can also manually update the attendance status.