QR Code

On the JED one of the highlighted features listed is the ability to generate a QR code in Events Booking:
extensions.joomla.org/extensions/extensi...events/event-booking
Generate QR code support

Allow generating and inserting QR code into ticket and invoice
Using the generated QR code and an mobile application for checking in registrants.

Where do I find this function?

You can find the instructions in this thread at the very top.

joomdonation.com/forum/events-booking-ge...-2-1-0-released.html

Hope that helps,
Roger