Battery life of the device should be at least 20%
Make sure the update.app is the one of your device
Do this at your own risk!!
Download the firmware of the huawei device you want to flash or upgrade
Extract the zip file to locate the update.app file
Now create a new folder with name dload in the root of the sdcard
Copy the update.app file into the dload folder ( sdcard/dload/update.app )
Turn off device
Press and hold volume up + volume down + power button at same time for about 5 secs
A screen with progress bar of the installation process will be seen
The progress bar will update till 100%
When update process is complete, phone will reboot
Its always a good to factory reset the phone from settings after it boots properly.