Px4 VTOL with QGC and joystick

I am setting up a VTOL tilt-rotor drone. I need help with a tilting transition servo. I want to be able to autonomously do the transition when on a mission, and I want to manually transition for testing purposes. How do I physically connect the servo to the Pixhawk and how do I map it to a button on my Logitech gamepad using QGC?