How to enable I2C
How to enable I2C funcion on Raspbian:
Please run the following command after you start the Raspberry Pi
Select 5 Interfacing Options and then P5 I2C - Enable/Disable automatic loading. A prompt will appear asking Would you like the ARM I2C interface to be enabled?, select "Yes"
Select "Finish" to return to the command line and reboot your raspberry pi.