How to change the nav frequencies in the GTN 650?

I recently purchased the RXP GTN 650 and am using it with the X-plane 12, C172. I have 2 touch screen monitors running Air Manager with a knobster. I am unable to get the 650 to swap the comps to nav to tune the nav frequencies. The Garmin trainer would have you push the rotary dial on the bottom right however when I do this in Air Manager nothing happens. Suggestions?

Thank you