The agitator will be one of two types. The first can be removed by undoing a bolt that is accessible after removing the cap at the top of the agitator. You'll need an extension bar and socket to do this. The second type has a white button around half way down the agitator. Just press the button in gently and at the same time pull the agitator upwards, in the line of the driving shaft.
Warrick J, April 2008