On A 3-way, there’s an extra terminal, called the “popular.” Power comes in for the switch on the common, then two “traveler” wires connect the initial switch to the 2nd about the brass terminals. The switch is simple to include to an present Wiz system, but has quite minimal functionality. https://tysonbmtyc.mybuzzblog.com/14553362/details-fiction-and-smart-light-switches