How to pass through RC manual controls through Pixhawk

I am working on a fixed wing aircraft and am wanting to know how I can pass through manual control from my RC receiver into the Pixhawk (through the RC IN pin on the servo rail on the top) and have the individual channel controls output to channels on the top of the Pixhawk. I am using a HiTech Aurora 9 TX and an Optima 7 RX with all 7 channels connected to the Pixhawk with a Crius PPM encoder.

So far I have all of my control surface servos connected to the servo rail (Aux 1-6) with my ESC providing 5.5v. I can turn everything on, and I hear the servos twitch when I connect the battery to the 3DR power module, but am unable to control the servos with my transmitter. I have read a few things online about changing config settings in Mission planer to enable pass through mode on those servo channels, but i’m a novice when it comes to RC stuff and am still learning the ropes.

any help or tips would be appreciated!