Hi,
Exactly, first set the Airspeed type. You may need to adjust the scale and zero point later.
Next define the adc# used for input
Some servo output can be used for analog input, like the output5 that should be free.
Not sure about the exact ADC routing, adc0 and adc1 are used with sensor port.
For other adc assignments you may look at source code or find the right one by try and error.