In theory: you see the tournament topic, submit an application: "hello. I want to participate in your tournament, please register me." Then you download the map and the save file. And you try to complete the tournament condition as efficiently as possible - for example, defeat all enemies in the minimum number of days. You have to play from the save file. That's it. In general, you complete the map, make save files, and send the final save file (from the day the task is completed) to the tournament organizer. In practice: there are no tournaments.