Identify the cold-water line under the sink. If you aren't sure which line supplies the cold water, try turning on the hot water. Allow the water to heat up, and then feel the pipes under the sink. The pipe that isn't hot is the cold-water supply. Turn off the water after the cold-water supply has been identified.
Position the bracket for the under-sink water filter, and mark the holes for the mounting screws (Image 1). The bottom of the filter should be at least 3" from the bottom of the sink cabinet, and the bracket should be screwed into a wall stud if possible. If no wall stud is available, use hollow-wall anchor bolts or toggle bolts to secure the bracket to the wall. Mount the filter onto the bracket (Image 2).
Slide a compression nut and ferrule (provided with the filter kit) onto both ends of the water line. Connect the plastic hoses for the filter to the compression fittings (Image 1). Connect the hose from the valve to the inlet on the filter, and connect the hose from the faucet to the filter outlet (Image 2).