I am trying to connect the ice maker in the my refrigerator to the kitchen water line. I am not sure how to properly connect the compression nut and ferrell to the copper piping. How do I do it properly? Do I simply clamp down on the ferrell with a pair of pliers to connect it to the pipe?

The ferrell simply slips on to the tubing , the tubing will protrude through the ferrell by about 1/8" as you tighten down on the nut it will compress the ferrell against the tubing. Mike

Just slide the nut on your feed line then slide on the ferrell, push your feed line all the way in and tighten your nut. As the nut tightens it will compress the ferrell onto your line and form a water tight seal. That's why they are called compression fittings. If you have marred the ferrell (scratched it or damaged it) it won't seal. Don't over tighten the nut either just tight enough to form your seal without leaks. Good luck