You can download circuit and hex file here http://www.hobbyprojects.com/bluetooth-device-control/
1. First make sure your HC-05 Bluetooth Module is paired with your mobile. The default password for pairing is "1234" or "0000". Check the manual of Bluetooth module.
2. When you press ON button it sends the data "A" to Bluetooth Module connected with a circuit. Micro-controller turns ON the relay when it detects "A"
3. When you press OFF button it sends the data "a" to Bluetooth Module connected with a circuit. Micro-controller turns OFF the relay when it detects "a"
4. For voice command click on Mic. icon and speak "ON" or "OFF" to turn ON/OFF device (it needs Wifi or Data Connection)