Thanks! There’s no really formal procedure in place at the moment.
I suggest that you start by taking a look at the list of open issues at agriggio / ART / issues — Bitbucket, and submit a patch and/or a pull request if you think you can help with some of them. Maybe add a comment in the issue tracker if you decide to pick something up, so that I know that someone is taking care of it.
Best,
Alberto