How to lock screen without power button oneplus

How to enable screen lock without power button oneplus. How to lock phone by double tap in OnePlus ************************************************************************************ If you are really interested in my video please follow me on YouTube and Facebook …………………………………………………………………………………………………. Subscribe to my channel:    / channel   FACEBOOK GROUP:   / 411530109484518   FACEBOOK PAGE:   / itmagicsbd   ………………………………………………………………………………………………….. Background music:    / channel