On a three-way, there’s an additional terminal, called the “common.” Power comes in to your switch around the widespread, then two “traveler” wires connect the main switch to the 2nd to the brass terminals. DIYers mustn't, having said that, attempt operating new wiring them selves—that’s a job for an electrician. https://wiringtoswitches90892.newbigblog.com/41007880/5-simple-techniques-for-smart-light-switch-white-clear-frame