There are several check-in options available on the Kiosk display screens.
Enter Code: an attendee inputs a unique reference code
Scan QR: an attendee provides their unique QR code to scan
Register: links to a registration form from the Registration Element
Insert your printed/e-ticket: an attendee provides their unique QR code to scan
Scan this code via event app: an attendee uses the QR Scanner on the event App. It also requires an attendee to be logged into the event App
If any option is not relevant to your attendees (or event) you can remove them from the Kiosk display screen by editing the screen options in the Core.