Communication between drone and GCS

Hi, I’m a beginner at drone.
I want to send a command from GCS (laptop) to drone in air via telemetry radio. I know the protocol used is MAVLink.
However, I am confused about how to start. I have found that there are drone kit, MAVProxy, Mission Planner, QGroundControl but I have no idea how to relate them. I would appreciate it if someone can give me an idea or procedure with details.
Thank you.