Copy the texture folder into your KCAI Citation Excel/XLS folder structure and amend the aircraft.cfg with a new entry in the format shown in the aircraft.cfg file included in this zip. The [fltsim.x] entry's number should be changed to one that is beyond the last one in your aircraft.cfg, so if that number was 166, the next entry must be 167.

You can then create or assign flightplans to the aircraft to get it visible in the simulator.

Any question, I am present on aitraffic.ch and will look for queries there periodically

If you are an FS9 user, there are separate textures for that platform included in a subfoler, and you should use those rather than the DDS ones.

Yanis