Good morning. Thank you very much, StatGrid, for answering me. I'm glad you got back to me. So can you tell me that there are already custom airports ready to be played, right? Where can I find these custom airports and add them to the game? I confess that I would like to customize an airport from scratch, but as you said, it can be complicated. Is there a video or tutorial teaching how to customize or create an airport?
Yes, ready-to-play airports are shared by other users of Endless ATC, see https://github.com/EndlessATC/Airports (click 'final' to browse airports) or https://discord.gg/v4wDGh3 if you use discord. These communities are maintained not by me, but by fans of the game.
There's not a video to explain it, but once you find the correct /location folder of the game, copying txt file(s) to it is straight foward.