Ignore what Peeps said. The aim of the game is to score goals. Lots of goals. Preferably more than your opponent, but definitely lots.
It's pretty easy really, i picked it up with no problem. The only difficulties lie within the limitations of the game. For instance, it won't let you have more than 4 strikers. How on earth are you supposed to score goals with only 4 strikers!?
Still, everyone should give it a try. It doesn't really take up much time at all, you spend about 5 mins twice a week selecting your team, although obviously you can spend more time contributing to the 'banter' if you like.