1. To open the configuration tool, simply run the following from the command line and follow the steps below.
    Note: I have used RaspbianOS Jessie (Released: 2016-09-23) for this tutorial.
    sudo raspi-config

  2. Select "Advance Options" then "Select" and press space bar.

  3. Select "I2C" then "Select" and press space bar.

  4. Select "Yes" and press space bar to enable I2C.

  5. Select "Ok" and press space bar.

  6. Finally, select "Finish" and press space bar to close the tool.