You can purchase Creatine from most health shops. Creatine is generally used by bodybuilders and gym users. When we lift weights or do heavy exercise, our muscles lose creatine and we feel less able to carry on.
Creatine supplements supposedly allow users to exercise for longer and make recovery times shorter. I don't think you should take Creatine for long periods of time and you should be careful about how much you take, as excessive use may cause liver problems.
Maybe you should join some muscle forums, like www.mickhart.com, where there are people who know more about these types of supplements.