So you want to activate the roll control so the rear brakes don't engage, correct? If that's the case the outlet for the rear (out of distribution block) go into the "in" on the unit, then "out" to rear brakes.
You would need to activate the unit before stepping on the brake pedal keeping fluid out of the rear (I think, lol), then press on the brake pedal to activate the front brakes.
I have mine installed on the front, I press the pedal, apply the button and release the pedal. My back brakes are now free. The front remain locked until I release the button.