How to enable or create notification for Users?

I assigned to a task into an user from admin section.Then I logged in that user section.But I can’t see the notification in user section.
I want to see notification in user…

Hi,
maybe this is of help:

can you please explain the second option…
In the second option:
That code want to edit which file?

It’s a regular logic hook, I guess this documentation will help you: