To Submit your game to the jam, click on the Submit Your Project button at the top of the jam page before the end of the jam period. 

Make sure to read the submission rules and adhere to them. 

If you are submitting an existing game that is hosted on Itch, select the game you wish to submit from the dropdown menu. Otherwise, provide a link the the previous version of the game (if applicable) and select "Upload Game" under the "Create New Project" header. Once you have created the new game page, return to the jam page and select the game for submission!  

That's it! Remember, you can update the game all the way until the last second of the jam submission deadline! Happy Jamming!