update pairing docs for 200403v2-b (Koenkk#2541)

Author: MathiasReker

docs/devices/200403V2-B.md

@@ -24,6 +24,10 @@ pageClass: device-page
 
 <!-- Notes BEGIN: You can edit here. Add "## Notes" headline if not already present. -->
 
+### Notes
+
+To connect the relay to Zigbee2MQTT, rapidly press the reset button four times in quick succession. The bulbs connected to the relay will blink five times before remaining steadily lit, indicating successful pairing.
+
 
 <!-- Notes END: Do not edit below this line -->