In order to get started with Android you will have to obtain a projectNumber and an apiKey Bellow is a snippet from the official Android documentaion:
To create a Google API project:
- Open the Google Developers Console.
- If you haven't created an API project yet, click Create Project.
- Supply a project name and click Create. Once the project has been created, a page appears that displays your project ID and project number. For example, Project Number: 670330094152.
- Copy down your project number. You will use it later on as the GCM sender ID.
To enable the GCM service:
- In the sidebar on the left, select APIs & auth.
- In the displayed list of APIs, turn the Google Cloud Messaging for Android toggle to ON.
To obtain an API key:
- In the sidebar on the left, select APIs & auth > Credentials.
- Under Public API access, click Create new key.
- In the Create a new key dialog, click Server key.
- In the resulting configuration dialog, supply your server's IP address. For testing purposes, you can use 0.0.0.0/0.
- Click Create.
- In the refreshed page, copy the API key. You will need the API key later on to perform authentication in your application server.
Note: If you need to rotate the key, click Regenerate key. A new key will be created. If you think the key has been compromised and you want to delete it immediately, click Delete.
Reference official documentation