Just so everything is clear, CONTRIBUTORS ARE NOT ADMINS! Anyone in the Founder and Co-Founder slots are admins.
Contributors are the much-loved veterans who regularly submit brilliant work to the group.
To become a Contributor, you need to do... well, that.
(You don't have to post every day or every week, but it's better if you don't become inactive for long periods of time)
You can either wait for somebody to promote you, or you can ask us.
Becoming a contributor is NOT easy, so don't be offended if we say no to your request. Just keep trying. The admins are happy to help out.