This page shows how to get the notification system running in your unreal engine 5 project.
Implementing the user interface
Open up the Content Drawer -> Right Click -> User Interface -> User Widget, name it WBP_HUD or something by preference.
If you have an existing HUD display in your project, you should use that one instead of creating a new one. Having multiple widgets on screen can reduce performance.
Place the WBP_NotificationPanel inside the HUD and anchor it to any position you want.
Inside your player controller, on begin play, create the HUD and add it to the viewport.