There's no specific way to make games on itch.io, but you can use any engine or language. And the best doesn't exist. Best for whom? For what kind of games? But people discuss this subject a lot, see other active topics in this category.
Why ask me? They must have license terms on their site. From what I heard you only have to start paying them if your game makes thousands of dollars or some such, so you should be able to download it and get started for free.
