To send Push Notifications on Android you need to have a Sender ID and a Firebase Cloud Messaging (FCM) Token or a Server API Key. Details on how to generate these required credentials are given below.

Get Google-Service.json

Go to the firebase console by clicking here.

If you currently have no projects created, create one. 

Now navigate to the project settings.

Next step is to add your app to the Firebase project:

Now download the Google-services.json associated with that app

Download the Credentials:

At the top of the page, just under ‘Settings’, click on ‘cloud messaging’. This will bring you to the page that shows you your cloud messaging credentials. 

Once you have located your Firebase Cloud Messaging credentials log into your XtremePush dashboard on xtremepush.com. Go to your project home and navigate to Applications and on the right-hand side click the "Settings" link next to the relevant Android application. Paste your Sender ID into the FCM/GCM Project Number (Sender ID) field and either the Server Key or the Firebase Cloud Messaging Token into the API Key field and click save.