Ionic, pushing notification outside of the app itself

Hi, I am also working on another project. The aim of this project is that I want to be able to push notifications outside of the app, the notification would be reflected on the phone outside of the app itself even when I close the app.

Photo for reference

I do not have much rough idea on how to start on it, any help would be deeply appreciated, thanks!!

Then read the docs to point you in the right direction: Push Notifications - Firebase | Capacitor Documentation