How to reach the state of "Ready to fly" and connect a Joystick to QGC

Hi, I have an unmanned submarine (it is not Ardupilot or PX4) and I want to customize the QGC to use it with my robot.
I connected my device via UDP connection and now I see that the vehicle is on state “Not ready”, what I need to do in order to reach the state of “Ready to fly”? where can I read about the states?
Second, I try to connect a Joystick to the QGC (via USB) and when i connect it, it doesn’t appears on the vehicle setup. is it connect to my first problem? or maybe I need to change another thing on my device. (When i used the mock link and connect the Joystick it does appears on vehicle setup)