How to calibrate ESC with joystick?

PX4 Autopilot Configuration & Flight Modes ⚙️
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i want make my own ROV. i’m using QGoundControl, use ArduSub firmware, use Odroid XU4 with ubuntu mate 16.04 and for controller i’m using joystick connect to Odroid, ESC Turnigy 30A

link https://www.ardusub.com/

but i dont understand how to calibration ESC using joystick, can anyone tell me how to do that?