1. If you're using a Kun Original or Super, you'll need to put on the "feet" (the rubber-covered parts) yourself. (The Kun Collapsible, Bravo and Voce come assembled.) The shorter screw goes into the L-shaped "end member" on the higher/wider end, and the longer screw goes in the lower/narrower end of the shoulder rest.
2. Use the screws that hold the feet to adjust the height of the shoulder rest.
3. Turn your instrument back over and try it out. If it's not comfortable, it needs to be adjusted, until you reach your desired position.
4. Turn your violin or viola over and slide on the assembled shoulder rest very carefully. Be sure you're putting the wider end of the shoulder rest on the side of the violin that will rest on your shoulder when it's turned over again, so that the narrower, tapered end curves down onto your chest. Using both hands, slowly work the shoulder rest up the back of your instrument.
5. If you adjust the shoulder rest up or down the back of the instrument, you might need to adjust the distance between the feet to ensure that the rest clings securely in its new place. To change this distance, adjust the L-shaped end member horizontally along the base member using the holes (Original, Collapsible and Bravo) or sliding mechanism (Super and Voce).