```dart{4-21}
@override
Widget build(BuildContext context) {
  return Authenticator(
    signUpForm: SignUpForm.custom(
      fields: [
        SignUpFormField.username(),
        SignUpFormField.password(),
        SignUpFormField.passwordConfirmation(),
        SignUpFormField.email(),
        SignUpFormField.phoneNumber(),
        SignUpFormField.address(),
        SignUpFormField.birthdate(),
        SignUpFormField.familyName(),
        SignUpFormField.gender(),
        SignUpFormField.givenName(),
        SignUpFormField.middleName(),
        SignUpFormField.name(),
        SignUpFormField.nickname(),
        SignUpFormField.preferredUsername(),
      ],
    ),
    child: MaterialApp(
      builder: Authenticator.builder(),
      home: const Scaffold(
        body: Center(
          child: Text('You are logged in!'),
        ),
      ),
    ),
  );
}
```