You might find more help on the ArduPilot project's discussion areas (or whatever flight controller you are using). HITL is really an exercise in hardware integration - the same principles apply that are used in the SITL implementation, but they have to be configured for the controller, and the controller has to be properly set up to substitute simulated inputs and outputs. We provide RealFlight Link, but how you talk to it is up to you.
It's very possible that Tridge and the ArduPilot crew have a standing solution for using RealFlight, but we haven't studied it or tried it.
