Go to https://firebase.google.com/ and create an account if you don't have one yet, then login and go to the main console.
Select an existing project or create a new one.
Create a "Firebase Realtime Database" if you don't have one already, make sure that the database has read permissions set to true in the "Rules" section.
Go to the "Overview" section and click the "Getting Started" icon for web projects.
Go to instadeq and open an existing visualization or create a new one, in the Source section select the Firebase type.
Enter the project ID and check that the other fields match, enter the API Key and Messaging Sender ID and click the green button.
Go to the Data section in instadeq, you can now make changes to the Firebase database and observe the updates in the Data section, you can use the API to make the changes or go to the Database section in the Firebase Console and make the changes manually.
If you need to get only a part of the database when it changes, you can edit the "Ref Path" field on the Source configuration and enter the desired path.