Help with wiring up RC

First off, I know this isnt a car, however I really need help with wiring stuff up. I just bought a used at9 transmitter for my rc plane, and the throttle input is set to the back slider. How do I change this back to the throttle being set to the stick and not the slider?

Update: I cant get anything to work. The channels make no sense. I'm new at this, but come on this is crazy. I plug a servo into the 2nd channel, and I try to move any of my control sticks and nothing happens. When I plug one into the 1st channel the stick that should be my throttle becomes my elevator, yet when I plug my esc into the first channel nothing happens. WHAT THE HECK?