The easiest thing is to contact the domain owner and/or the organizers. Contacts are usually here, but the most relevant are in the announcements of the game itself. Experienced players or authors themselves will tell you what you need, how to start and all the subtleties.

Yes, on the domain try.en.cx there are ready-made and open-to-play intelligent online games where you can get acquainted with the game engine and with examples of tasks.

If nothing is clear at all, contact the Technical Support of the network, they will tell you general questions and who you can contact in your city.

If you want to create a game, first discuss it with the domain owner or administrator. Next, they will give you access to the engine and tell you what to do and how to do it.