1) Download the Arduino 1.0.3 IDE from http://www.arduino.cc/en/Main/OldSoftwareReleases
2) Download the "WiFiLightSwitch.ino" file from https://drive.google.com/file/d/0B0jlZyidYM9jMVBJTW1GMHI4X1U/view?usp=sharing
3) Modify the .ino file to include your WiFi credentials.
4) Upload the .ino to the Arduino and open the Serial Monitor to obtain the IP address assigned.
5) Download this app and enter the IP address assigned to the Arduino.
6) You can now control the LED from your device over the network.