If you use unity then I have found a video on YouTube for uploading the game to itch.io but The unity side is probably outdated, but it should still be easy to follow:
https://www.youtube.com/watch?v=ONMCHZ1Bv50
Once you have figured out how to upload to itch, the rest is just on how to submit it to this jam.
I think that's easy. once the jam starts, a button that let's you submit one of your games will become available.
If you still have trouble by then, I don't mind trying to make a short tutorial with screenshots for people.
I hope that helps!