Send ionic push notifications from angular app

Hi, I have a Ionic v1 mobile application and an angular webapp for the administrator.
The administrator need to send notifications to smartphone application users so I followed this guide to add the notifications support to the ionic app and I can receive notifications created from dashboard.
Now I need to send the notification automatically from the angular app when some eventa happen.
How can I do this? Should I have to use api?
Thanks in advance,

Davide C.