app lock

[Abhilash28]

Please enable app lock feature on m51

[Ehsank]

If you want to use app lock from Samsung then download "S secure " from galaxy store ,

http://apps.samsung.com/appquery/appDetail.as?appId=com.samsung.android.app.sprotect

Otherwise you can download other good app lock from playstore

https://play.google.com/store/apps/details?id=com.domobile.applock.in

[Sidhabhi]

Try S secure from galaxy store

[ChandanMallick]

Go for S secure if you don't want to use then use activity launcher to use the inbuilt app lock