Note: Make sure there is 50% or above power left before the update.
Download the update.zip
Don't change the zip name and do not unzip it.
Copy it to the root directory of SD card or internal memory. Remember it is the root directory.
Make sure the phone is powered off.
Keep the volume up and down keys pressed first, then press the power button together, untill enter recovery, release.
Install the update zip
wait it to start.