Controlling an aircraft with a gamepad brings a funny challenge - the throttle. Because the throttle stick on a normal transmitter latches or doesn't spring back to the middle, it's a pretty hands-off stick, usually.
It's pretty easy, though I believe you need an amateur radio licence to use an SDR transmitter, or something that can generate the PPM signal for the transmitter module you're using.
The whole system would be like this, if you want to get fancy and do FPV.
Computer, has audio out connected to the PPM in pin of your tx module. There's an SDR plugged in to rx your video signal, with a decoding loop set up to display that video on screen. Your gamepad is plugged in, and another program takes your button and stick inputs, converts them to 4ch ppm, then plays that as a sound. Because the signal is what the tx module expects to see, it takes it and sends it. (Note to self: PPM signals don't sound nice, be sure the tx module is plugged in BEFORE you start sending data.)