OK, you'll look on the "front" of that plastic knob, and see a U shaped pice laying flush to the knob. The U shaped piece has small ribs in it. Push "out" (towards the outside of the car) on those ribs, and the U shaped piece will slide out. That will remove the retainer, and the knob itself will slide off towards the rear of the car. Hard to explain, easy to do. As long as you know about the U shaped piece you'll figure it out.

Gilly