basically it's a lot of dancing. they have a few choreographed movements which they teach to a room full of people, and then you do it in waves while other people watch. sweaty!
good fun, they explain a lot about the spirit of the olympics and what they're trying to achieve - but not what they're looking for: "just enthusiastic, happy people we'd want to work with"... i suspect that if you have some dancing ability you'll be way ahead - good luck!