I can’t authenticate firebase by following the Steps

Question

private lateinit var auth: FirebaseAuth

class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        auth = Firebase.auth
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        supportActionBar?.hide()

        val menuNavBottom: BottomNavigationView = findViewById(R.id.bottomNavigationView)
        val navController = findNavController(R.id.FragmentContainerView)
        menuNavBottom.setupWithNavController(navController)
    }

    public override fun onStart() {
        super.onStart()
        // Check if user is signed in (non-null) and update UI accordingly.
        val currentUser = auth.currentUser
        if (currentUser != null) {
            reload();
        }
    }


}