How do I enable the lock icon to lock app in recents

[AC Question]

In nougat on Samsung s7. It says you can lock an app in the recents.. But I have no luck icon on any apps?

 

[ManiacJoe]

If by "lock" you mean "pin so that the user cannot exit the app", it is a feature that you need to turn on in the phone's settings: / general / security / screen pin