First turn your phone off, then follow the instructions provided - it is impossible to update the phone while it is still turned on. After plugging the phone in with the volume down button held, the LED should turn yellow-green, release the button when you see it and the updating procedure will commence automatically. Obviously, do not disconnect the phone until PC Companion clears you to do so.
Should something go wrong and your phone get stuck booting up for hours (i.e. bootloop), force it to shut down by pressing and holding both the power and volume up buttons simultaneously until three vibrations are felt. Then allow it to charge for a while (don't turn it on) before you try repairing the phone with PC Companion. Hopefully it never comes to that.
Also kindly go easy on the caps lock and punctuation marks.
