No need to 'change' it to an ai.

All thats needed is to add it to the flightplans using TTools.

Rather than me explaining the steps, your better off to read the help file that comes with TTools. There is a section that fully explains adding new aircraft.

Just one note, highly detailed flyable aircraft can put a drain on your system (FPS). It is most often better to find a similar a/c designed specifically for ai.

Dave