The SITL (software in the loop) simulator is a software on XBLink allows you to run Plane, Copter or Rover in your specific location without any hardware.
This allows ArduPilot to be tested on a very wide variety of vehicle types:
Multi-rotor aircraft
Fixed wing aircraft
Ground vehicles
Underwater vehicles
Antenna trackers
You can simulate a flight in XBLink by following these steps
Configure SITL software
In XBLinkApp, go to Dashboard tab -> Simulator
Configure your vehicle type and choose the location
Click Start Simulator button
The simulator will auto run in your XBLink, you should turn it off if you don't use it anymore by clicking button Stop Simulator
Change XBFirm telemetry input to Simulate Mode
By default, XBFirm is in Serial port telemetry input mode(The telemetry data will be received from the real flight controller), you should change it to Simulate mode
In XBLinkApp, go to Dashboard tab -> Telemetry Input -> Choose Simulate
Stop XBFirm, then Start it again
You should change the telemetry input mode to Serial port if you don't use simulate mode anymore