To send push notifications to Android devices, you must ensure a project is enabled with an Android push notification service. The push notification service that you can use for Android is Google Cloud Messaging (GCM), which requires you to create a Google Firebase project.

1. Login to Google Firebase console at https://console.firebase.google.com/.
2. Click Add project.
3. In the Project name field, enter a name for your project. For example, OAAAndroidPUSH.
4. On the Google Analytics for your Firebase project page, deselect Enable Google Analytics for this project, and then click Create project.
5. Click Continue when your new project is ready.
6. In the left navigation pane of the project window, click the Settings icon, and then select Project settings.
7. On the Project settings page, click Cloud Messaging.
8. Under Cloud Messaging API (Legacy), click on the ellipsis and select Manage API in Google Cloud Console.
9. In the new tab that appears, under Cloud Messaging click ENABLE.
10. Return to the original tab where you clicked Cloud Messaging API (Legacy) and refresh the page.
11. Note the values present in the Server key and Sender ID fields. These values are required later in Configuring OAA Properties for Android Push Notification using Legacy FCM APIs .