If you're looking for an in-depth guide on how to make your first Castle game, check out the Make Your First Game tutorial. But if you just want to get up-and-running as quickly as possible, then you can follow these easy steps:
main.luafile in a text editor. You'll find it in the new project you created.
If you need any help with your game, feel free to stop by the Castle Discord. We're always happy to help!