Being my tiny dragoness self as a newby
There are many different people (generically called GM for GameMaster) running many different games in many different systems, including some that are "freeform" which use no rule set as such.
As Lord X says, the best way to find one accepting new players is in Players Wanted. Or you can post in GM Wanted and request a game in a system or of a sort that you would like to play.
You'll also want to peruse the FAQs and make sure you are aware of the site rules and customs.
Happy gaming!