Well that's me stumpedThe nut and olive are not used to connect to the white tap connector, screws straight in ,rubber seal should be in the brass nut of the tap con. So after turning water off and draining down ,you undo the flexi hose off ,then unscrew the brass reducer from the tap con. Check rubber seal in place and screw in isolator. Is the new iso same thread both ends ? If it is you will need another part to connect the flexi hose to the isolator.