How do I install under cabinet lighting?

How heavy is it? Generally speaking one screws it into the bottom of the cabinets.

The lighting normally will fasten to the cabinet in some manner specified in the package. It may be short screws or even double-sided tape, depending on the weight. However, getting power to the lights is another matter. Battery operated LED fixtures would be the easiest. If you need 120 VAC power supply, you should get an electrician. Power would come from a local wall plug and wires would be routed up inside the wall and out through the back of the cabinet or edge under the cabinet.