Go to settings > developer options > there you can see Super user setting click on that and select the option always allow. Then install SuperSU from Google play store and let the supersu’s binary update then you are rooted. Then open supersu and go to setting and scroll down to the option access > and set Default access to GRANT. Then you will have full root access, if you forget to give always allow and grant then your application which needs root will hang. Do not give prompt as option always allow and Grant will do..