Using a Behringer X-AIR series Mixer (XR12) for TX audio processing

XR12 -X-Air series mixer - how I setup and use my XR12 for audio processing of my TX audio - into the Expert Electronics SunSDR2DX- Using Pr781 mic-into the XR12- out of AUX1 into an audio isolation transformer (or direct box) to Mic input of the SDR transceiver