The knob is attached to the potentiometer with super glue. It's really simple, if your knob is loose, then it should pull straight off the bottom of the inhalater, exposing the potentiometer. Turn the knob over and you'll see the little hole that they put the super glue in. Add one or two drops(dont over do it!) super glue into the hole, pop it back onto the inhalater(make sure it's lined up!) and press firmly. Let it sit for 20 minutes and you're good to go. As for the cap... Taylor is right... push on it from the side and it should pop off with little effort. Pulling it straight off is MUCH more difficult.