The basics are follow the xlights/vixen/fpp mapping channels.
In fpp, you direct them out the appropriate device (likely e1.31).
The actual port setup is done on the falcon.
If you decide to do it in xLights, you can upload the config to fpp and the falcon. The models have channel mapping/port config and that corresponds to what you setup on the networks page. Found a video:
https://m.youtube.com/watch?v=NsT80wYkEAg
there a bunch out there. If this one doesn't help, watch one of the others.