1. Download the rooting file which is required to root your device and place the file onto your desktop.[Here]
[Make sure you don’t extract the file]
2. Copy the .Zip file into your SD card.
3. Then turn off your mobile and connect your device to the PC through USB cable then restart the mobile in recovery mode.
[How to– Connect the device with USB cable then hold the Volume Up button[+] and Power button simultaneously till you find a logo.Then press the menu which is beside home button.]
4. You find a few options on the screen, select the option called install zip from SD card.
5. Select Root-i9001-Signed. Zip and select yes. [Power button to select ]
6. Wait until the process complete [Around 2mins]
That’s your device it will reboot and you will find superuser app in your applications.