Why I cant put an info in lockscreen?

[dragonela alabata]

I want to put information just incase my phone lost somewhere

 

[SpookDroid]

That would depend on the specific phone you're using; not all phones allow to display custom contact information on the lockscreen.

If it does, the option would be in the phone's Settings where you set up your lockscreen for PIN/Password/BioMetrics etc. and in devices that support Always On Display it should also ask you if you want to display in both lockscreen and AOD or just one of the two.