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.
Setting up your Firebase Cloud Messaging Key
Go to https://console.firebase.google.com/ and if you don't already have one, make a project.
When on your project overview page, in the top left-hand corner you will see your project name, and beside it a settings cog. Click the cog, which will produce a new menu from which you select ‘project settings’.
You are now in the ‘general’ tab, in the settings menu.
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.