Press and hold the Smappee's button on the side. Watch the color change to purple. Release the button at purple, Smappee should be blinking purple.
Press the WPS button on your Router.
Smappee will return to the Green hartbeat after successful connection with the new Wi-Fi network and parameters.
If Smappee could not connect, it will show Red!
Note: if your router does not have a WPS button, the Web Interface or Utility generally provides that function. This is the case for Apple's Airport Express routers. Go to the Airport Utility and select WPS.