In order to be able to send push messages to your app, you need to have certifications from Google's Firebase Cloud Messaging (FCM).
Obtaining Firebase Cloud Messaging credentials
1. Log in
Log in to your developer account at the Firebase Console.
2. Create project
If you already have a project, proceed to Step 3. If you do not have a project, click Add project.
Enter the name for the project and click Continue.
If the app is to use Google Analytics, keep it enabled. If not, disable the feature and click Continue. Once the project is ready, click Continue again.
3. Find credentials
In the Project Settings, locate the Cloud Messaging tab.
Copy the Server key token to your clipboard.
Please make sure to copy the Server Key and not the Legacy server key.
4. Add the tokens to your app in Mobile Engage
In Mobile Engage, locate the Apps tab and click Edit by the required app.
In the Platforms section, click Edit again to enter the Android Platform settings.
In the window displayed, add the Server key to the Google Cloud Messaging API key field and click Confirm.
5. Add Firebase json file to app
In the Firebase > Project Settings, locate the General tab.
At the bottom of the page, click on the Android symbol.
Enter the Android package name. The package name is the applicationId in your app-level build.gradle file
It is important that the Android package name in Firebase exactly matches the applicationId used in the app or push message campaigns will error.
Click Register app.
Download the google-services.json file and move the file to the app folder of the app. Then click Next
Update the project-level and app-level build gradle files to use the plugin, as detailed by the Firebase instructions.
Sync the gradle files.