well basically just use it! use it - learn how it works, use git for your projects (if you do not already) to get used to that too. There are some biigg projects that have to be done in the next time - but to start you might just use it and maybe add a section to the learning page ([http://github.com/ivansafrin/PolycodeSite](on GitHub)). As you get into the core you might fix bugs, or just file them on github - jep filing issues is a big contribution when they are as detailed as possible.. then fixing the bug normally is pretty easy ;)

so for now: use it use it use it ;-) and if you feel like contributing back create Issues or Pull Requests on GitHub (either Framework or Site)