Slow down. This is a month-long jam.
Go back to the main page for the jam and read it carefully, especially the part at the top. You can do two things in advance, but they are not required:
- Create a GitHub repository for your project.
- Create a project in itch.io
Both of these should just be placeholders. Starting any other work before the theme is announced is frowned upon, and in some cases can get you disqualified.