Download SuperSU to root your device.
Now move the SuperSu zip file to the root of your internal memory.
Turn off your phone.
Boot your phone into recovery by pressing “Volume Down + Power” button simultaneously. (In some phone, you can access the recovery menu by pressing “Volume UP + Power” button)
In TWRP Recovery, Click the INSTALL menu and Browse and Select the SuperSu Zip
Now Swipe to Install SuperSu.
Yes, Now the root must be working if you properly installed.
To verify, Go to Google Play and download the Root Checker app to check the root status. If root checker app says root access available then Enjoy you have root on your smartphone.