It's very easy to mirror or extend your desktop in macOS with AirPlay to AirServer.
Mirroring your desktop with macOS:
- Press the AirPlay icon in the top menu bar and choose your AirServer receiver.
- This will automatically mirror your macOS screen to AirServer.
Extending your desktop with macOS:
- Press the AirPlay icon in the top menu bar and choose your AirServer receiver.
- After the connection is made, select "Use As Separate Display".