Unplug the washer's power cord from the wall outlet.
Pull the knob straight out as if you were starting the machine. Twist the knob 180 degrees so that the U-shaped portion of the knob's retaining clip is facing the edge of the machine.
Insert a small hooked tool underneath the flange of the knob from the edge of the machine. Work the hook into the U-shaped portion of the clip. Pull the tool straight out toward the edge of the machine to slide the clip out. Set the clip aside.
Pull the knob straight off of the control panel.
Flip the replacement knob over so that you are looking at the underside. Locate the slot in the shaft of the knob. Insert the clip into the slot until it stops.
Push the hole in the shaft of the knob onto the timer shaft protruding from the washer control panel. Push down on the knob until the clip snaps into place. Pull up on the knob to ensure it is secured to the shaft properly.
Plug the power cord back in.