Unscrew your existing wall switch from the back box. Take a photo of the wiring for reference. Disconnect the live wire (usually Brown or Red) and the switched live wire (usually Blue with brown tape, or Black with red tape).
Insert the live and switched live wires together into the terminal connector block provided by Retrotouch and tighten the screws. This keeps constant power going to your smart bulbs so they can always be reached by the Hue system. Tuck this connected block safely into the back of the wall box.
Decide if you want a single large button (1-Gang) or two split buttons (2-Gang). Snap your preferred button layout onto the plastic Retrotouch insert frame. Ensure the arrow marked "Top" on the back of the switch mechanism points upward.
Screw the Retrotouch backplate directly into your wall back box using the standard plate screws. If you are sticking it directly to a wall without a back box, use the included 3M adhesive pads instead. Finally, clip the glass front faceplate securely over the mechanism.
Launch the official Philips Hue app. Tap Settings (the gear icon in the bottom right corner) -> Accessories, then tap the large plus (+) icon to add a new device.
(Do not choose "Hue Dimmer Switch.") Scroll down the list of options and select Friends of Hue Switch. From the list of brands that appears, select Retrotouch.
The app will display an animated graphic showing you exactly which button to press (usually the top-left or top-right rocker).
Press that specific button down firmly and hold it for a full 10 seconds without letting go.
Note: Because it uses kinetic power, you need to push hard enough to click it fully so the internal radio fires the pairing signal.
Once the app flashes a "Success" message, it will prompt you to name the switch. You can then map the 2 or 4 buttons to control specific rooms, cycle through your favorite color scenes, or act as dimmers.