Android Question Images and buttons in Firebase Notifications

Hello,
I've started working with Firebase Notification messages successfully following the various guides.
Now I want to add images and buttons that show directly in the notification and I'm a little confused on how best to do that.

Here's a guide I've found with a sample of a possible result:
https://www.pluralsight.com/guides/android/push-notifications-with-firebase-cloud-messaging

Thanks
Andrea