They're pretty easy to install. I covered the fenders with masking tape, then used a couple clamps to hold the flares in place on the fenders. Then trace the flare opening and cut just above that line.
For the rear most part of the rear flares, cut right up to the inner fender support without cutting into it. This will put the front of the flare almost flush with the inner fenderwell.
For the front flares, the cut line at the back of the flare will be almost flush with the inner fenderwell.
I used a jigsaw to cut mine.
