Thanks hotneil. I took another look and discovered there is an indentation in the floor of the CD drawer that holds an MP4 disk. I did not know that.
Now that I have looked at the installation instructions, I see how to do this (I think). The fixed wing planes, tie the sound to the throttle, which we do not want for a helicopter. A helicopter is brought up to Flight Idle (IU1) and the governor keeps it there. It does not have the louder, softer sound of an airplane engine.
So, we can hook the engine sound up to a knob, turn it on for startup and low idle, then advance it to the faster speed and leave it there. After landing, just turn it down and go to shutdown sounds.
There is pilot chatter and gun sounds too, but you need a separate channel for each one. Good thing I have a DX-9.
Jim