Follow the following procedure:
Install Universal Android drivers for your PC.
Download and run VRoot after connecting your phone to the PC and enabling USB Debugging under Settings>Developer options.
Click on the green button that (probably) says Next, in Chinese.
The software finishes in around 10 seconds, and your phone reboots. Also the software displays a Success symbol. Now, you may install Chainsdd Superuser app from the Play Market. Alternately, you can keep using the Chinese Superuser apk that’s automatically installed. If you do install Chainsdd Superuser apk, make sure that you update superuser binary too.