First of all you need to initialize the angularfire modules in your app module like this:
const firebaseConfig = {
apiKey: 'XXXXXXXXXX',
authDomain: 'XXXXXXXXXX',
databaseURL: 'XXXXXXXXXX',
storageBucket: 'XXXXXXXXXX',
messagingSenderId: 'XXXXXXXXXX'
};
You can get this keys by signing on firebase and creating a new project.
imports: [
AngularFireModule.initializeApp(firebaseConfig),
AngularFireDatabaseModule,
AngularFireAuthModule
],