I watched that video a few days ago. It was a good start.
I was just thinking of also adding:
On an open field, fly around 30m away, and around 10m high (below RTH altitude). Trigger RTH and get familiarised with the idea that the Mavic can return to home on it's own. It should go up to RTH altitude, and fly home.
If it starts flying away instead, you can cancel and take control and bring it back manually, and maybe check calibration after landing. Better test this RTH feature when it's nearby than to watch it trigger on its own far away and freak out.