So I am guessing that you have 5 or 6 wires between your Spectrum receiver and the Wookong; so you have A, E, T, R, U, and maybe X2, all wired, and that X3 is NOT connected on your Wookong. (Please correct me if I am reading in between the lines incorrectly.)
Connect the X3 to a spare channel on your receiver (maybe channel 7?). Now assign one of your free controls on your AR8000 to channel 7 output (if that was the free channel). If you are using a slider or dial, then the center position should be the "don't move" position, and moving to either direction will tilt the camera up or down, fast or slow depending on how much it's turned. If all you have is a switch, then you'll need at least a 3-way switch to tell the gimbal to go up, down, or no movement.
As for the specifics on how to assign a control to a channel, I can't help you with the Spectrum since I don't own one. Others on this forum can help you with that detail.
I hope this is helping...