To install LED strip lights under a kitchen cabinet, apply double-sided tape to the lights, switch and adaptor, mount the adaptor and switch, apply double-sided tape beneath the cabinet, mount the light strip, and plug it into the switch. The required supplies are mounting tape and scissors.
Set the LED adaptor and light switch on a flat surface with the back sides up, and cover them with strips of strong double-sided mounting tape. Do not remove the paper strip on the exposed side of the tape. Choose an adaptor mounting location on the underside of the kitchen cabinet, remove the adaptor's tape, and press the unit up into the cabinet floor. Use firm pressure. Remove the tape paper from the light switch and mount it under or directly next to the cabinet.
Stretch a length of double-sided tape down the middle of the cabinet underside. Run your hand over the tape to press it into place, and then peel off the paper covering. Plug the LED strip into the light switch, and press it up into the cabinet tape strip. If you are placing multiple light strips, connect each one to the strip before it, and then mount the lights one at a time.
Connect the final light strip to the toggle switch, and plug the adaptor's power cord into the nearest electrical outlet. Flip the light switch to test your work.