[applianceman]

Open the dishwasher and look at the back in the bottom of the tub. You should see a filter (screen) remove it. Under the filter is were the piston and nut is located. Using a pair of piers unscrew the old one and screw the new one back in and you’re good to go. Hope this helps.
http://www.appliance-repair-it.com/dishwasher-repair.html