On A 3-way, there’s an additional terminal, known as the “popular.” Power comes in to the switch around the widespread, then two “traveler” wires hook up the main switch to the 2nd around the brass terminals. In case you have Philips Hue bulbs, the Philips Hue dimmer can be employed https://wiringtoswitches32963.blue-blogs.com/42230280/5-simple-statements-about-smart-switches-for-home-explained