Your game should be submitted during the time of the jam. Once submitted, you can still make changes to your game and upload improvements / fixes, so do not hesitate in submitting early.
To submit your game, publish it on itch.io as a new game. The preferred format is to submit it as an HTML5 game: use export to HTML5 in microStudio and upload it as an HTML5 game on itch.io. This is the best way to allow everyone to test and rate your game, from any platform.
Optionally you can add downloadable versions for Windows, Mac, Linux but this is not required and does not provide any benefit for the jam.
Once your game is published on itch.io, go to the jam page https://itch.io/jam/microstudio-jam-3/community and create your submission entry.
You may also publish your game on microstudio.dev, but this is not mandatory.
If you have any questions about submission, please post them here!