Please have your Mac password ready, as you may be asked for it more than once.
Part 1: Download and open

Part 2: Let me see your screen

Part 3: Let me use your mouse and keyboard

Can’t find the settings? Click the Apple logo at the top left of your screen, then System Settings, then Privacy & Security on the left. The screen recording setting (part 2) and Accessibility (part 3) are both on that page. On older Macs, System Settings is called System Preferences.
I can see your screen but can’t move your mouse? That means part 3 isn’t switched on yet. Please follow the steps just above and switch on Getscreen under Accessibility.