Need Help :How to enable Capacitive Touch Buttons?

:crying::crying::crying: OPO CM12.1 : :crying::crying::crying::crying:

I have a new OPO with CM12.1 ( LP 5.1.1) , while setting up the phone for first time, i got the option of using Onscreen Buttons instead of Capacitive Touch Buttons . Which i selected . But now ,I want to get back to Capacitive Touch Button and thus want to disable the Onscreen Menu Buttons .
I could not find such option. Please help :crying: