Open the Settings app.
Go to Accessibility>Guided Access.
Turn the Guided access switch on.
Enable a passcode/Touch ID/Face ID for exiting Guided Access.
Open Merinio.
Press the Home button three times or the Side/Wake/Sleep button three times.
Tap Start on the Guided access bar at the top.
To exit Guided access, press the Home button or the Side/Sleep/Wake button three times.
Enter the passcode.
Tap End at the top left to exit Guided Access.