Android Push-notification configurations
A) Open the Firebase console and log in to it.
B) Navigate to your project in which you want to add the notification services.
C) Open project setting by clicking on setting button.
D) It will redirect to the settings of your project. Go to the cloud messaging tab to navigate to the messaging services of the Firebase.
E) Copy the server key and add it to the plugin of the application store.
F) Open the admin panel of your store and go to App Settings/API Settings.
G) Then click on the Push Notification tab.
H) Paste server key in android server key.
I) Then click on the update button to save changes.
Now you are done with the push notification services.
For more details documentation on push notification click here