Hello Chris,
Mainly, you have to model your airplane in AVL (which uses a vortex lattice method), and extract the stability derivatives. Then generate the CRRCSim model (.xml) by using these coefficients.
On the Paparazzi side, you have to define your sim method in your <aircraft>.xml (see the committed file) and run the simulator with nps while the CRRCSim software is open and waiting for nps commands. Thats it ! :)
We have only prepared the Funjet for now just as a reference A/C, but there will be more...
There are still some parts to change (especially the propulsion part in CRRCSim), we are working on it...
Cheers,