give commands by pc through arduino to R/C car remote throttle insterd of hand

I’m trying to control RC helicopter by it’s original remote.but want to control throttle via arduino uno by computer.how to do this.I just want to control throttle.I have add a photo of the throttle I want to control by arduino.i will remove that throttle switch and connect wires on poles and wire to arduino

.. a guess:
That looks like a potensiometer.. Check voltage range to find min/max. (center pin of the three)
Arduino (328) can do 32kHz PWM. This can be used to give you an analog voltage 0V..5V

A (active) low pass filer must be added to smooth the voltage.

you mean this?