1. From the thread link above, download both the TWRP.zip and root-stable.zip files and copy them to your sdcard.
2. Shut-down your device and then power on and go to boot mode and select recovery mode.
3. From the menu, navigate to APPLY UPDATE FROM SDCARD2. Select the TWRP.zip and install it then shut-down again.
4. Power up the device and go to recovery mode again.
5. From the TWRP Recovery menu, press the install button and find the root-stable.zip. This will root your device. Voila!
You can also use different ROMs here.