Replacing The Door Knob
Remove the c-clip from the back of the door spindle, you should be able to unwind it right out.
Once out, you can access the screws to remove the old washer & knob and put the new one on.
Screw the spindle back into the door and replace the c-clip.
You can purchase a replacement Pyro Fire door knob from the Pyro Fires website.