1. Download: Update.zip
2. Copy ZIP file to your SD-card
3. Turn off your phone
4. Now, you will have to switch ON your device in the recovery Mode which can be done by holding the Middle button and then Power ON the device by pressing the Power ON button.
5. In recovery mode, you will see the option called update from SD Card, select this option and then you will see that the list of files will come from which you will have to select the file which is named as Update.zip
6. Wait a few seconds (MAX 5 minutes!)
7. Your phone is rooted