There are two setup stages for Self Check-in for Event Guestsn.
First you need to turn on Self Check-In at the Event Category level
Then you need to activate it on each event you want to use it on.
Requirements
You must be an Organisation Admin to turn on Self Check-in for Event Guests at the Event Category level
The following users can activate Self Check-In on specific events
A user with permission to create events
An event manager
A project manager of the project that the event belongs to
An organisation admin
Steps
Select My Apps in the top menu
Select Event Categories
Press Edit next to the Event Category you want to edit
Scroll down to the Event Attendance section and tick the box to turn on Self Check-in
Press save
That’s it. Now you can activate Self Check-in on each event you create using this Event Category.