Send and retrieve a custom field in Socialize laravel 5

How can I sent a custom field in socialize laravel in RedirectToProvider method using this method. if ($social == 'facebook') { return Socialize::with($social)->fields([ 'first_name', 'last_name', 'email', 'gender', 'birthday' ])->scopes([ 'email', 'user_birthday' ])->redirect(); }

suppose i want to send network_id => 9.

And the how can I get it in my handler method where I am getting user information. $user = Socialize::with('facebook')->user();

via Chebli Mohamed