FCM send to specific user - google-cloud-firestore

Question

I am using cloud Firestore.
When I use cloud messaging to send push notifications to an app, a message goes to all users (users registered with Authentication) who are registered in the app.
The app has a login function, so I hope only the logged-in user gets notified.
That is, how can I send notifications only to specific users?
I want to set the time and day of the week with cloud messaging and send it to a specific device.
Now I even marked the token on the logcat and tested it in cloud messaging as shown in the picture.
However, the test cannot set the time and day of the week.
Is it possible to do this in the Fire Store? Or do I have to set the time and day of the week in the code as shown in the link?
enter image description here
//FirebaseMessagingService
#Override
public void onNewToken(String token) {
Log.e("NEW_TOKEN", token);
}
//MainActivity
FirebaseInstanceId.getInstance().getInstanceId()
.addOnCompleteListener(new OnCompleteListener<InstanceIdResult>() {
#Override
public void onComplete(#NonNull Task<InstanceIdResult> task) {
if (!task.isSuccessful()) {
Log.w(TAG, "getInstanceId failed", task.getException());
return;
}
// Get new Instance ID token
String token = task.getResult().getToken();
// Log and toast
//String msg = getString(R.string.msg_token_fmt, token);
Log.d("NEW_TOKEN", token);
Toast.makeText(MainActivity.this, token, Toast.LENGTH_SHORT).show();
}
});

Answer 1

I'll just write an answer just for better track.
As #Doug already mentioned, you could try using this code sample and try on your own.
Finally, is a good practice to show what you have tried and a code snippet to better understand your question.