You are project admin; use the tokens you remembered (hopefully you did when a user is getting the token in your app) in your database and send a push to all token in your database.
You are project admin; use the tokens you remembered (hopefully you did when a user is getting the token in your app) in your database and send a push to all token in your database
They do nothing other than to iterate through all users from your project and use their token to send a push to.
This is what you need to do. There is no method.
Away from that; when your users are using your app they are registering to a TOPIC (did you removed that line?). You can send to this TOPIC as all your app users did register to this topic.