You add content to clubs: images, videos, articles etc. You're also active in general there, answering questions and commenting on things. The more people who fan your stuff, and the more comments your stuff gets, the faster you ought to get a medal.
The system is a bit random though: some people get medals for a small amount of stuff, while others take longer. People sometimes get medals in clubs where they've been less active than the clubs where they've contributed more.
It takes a while, so you really have to be patient. It took me about a year of being active here to get my first medal. It's better to just contribute for the sake of contributing, and just let the medals happen.
