Pull the washing machine out so you can get behind it. There will be one or two flexible hoses connected to the water pipe(s). There should be a little lever which turns by a quarter turn where the hoses meet the water pipes. The levers are usually red and/or blue. You need to turn these to the off position before unscrewing the hoses. Then, unscrew the hoses at the washing machine end first. There will be a little water still in the hoses, so put a basin or something underneath before lowering the pipes to to catch the dribbles.