Firebase login for specific users

I'm trying to create a firebase web login system for only specific users(already added to firebase), I added my account to firebase authentication, and kept only kept:

  var token = result.credential.accessToken;
  var user = result.user;

}).catch(function(error) {

  var errorCode = error.code;
  var errorMessage = error.message;

  var email = error.email;
  var credential = error.credential;
});

But, it allows any user to login, is there any way to allow login for specific user? Sorry, this is my first working with firebase, and thank you and advance.