1. To get the API reference, refer to Documentation → API Reference → DELETE/POST /configuration/kiosk
2. To set it directly from the user interface :
a. Open the application you want to kiosk
b. POST /configuration/kiosk → Try it out→ Execute
3. To remove it directly from the user interface :
a. DELETE /configuration/kiosk→ Try it out→ Execute
Lock the application
$cmd activity kiosk start
Unlock the application
$cmd activity kiosk stop
Link to FAQ
More information on LockTask mode from Android DeviceOwner APIs