Getting auth_code

[axlrosebcsERP]

Hello everyone.. I would like to know or where can i get auth_code?

Below is the code that i get from github..

        string app_id       = "{{app_id}}";
        string app_secret   = "{{app_secret}}";

        var short_code = "{{short_code}}";
       
        **//Please explain to me how or where i can get the auth_code?**
        var auth_code = "{{auth_code}}";
        
        var auth = GlobeApi.Auth(app_id, app_secret);

        Console.WriteLine("Login Url: ");
        Console.WriteLine(auth.getLoginUrl());
        Console.WriteLine("");

        Console.WriteLine("Get Access Token:");
        dynamic access_token = auth.getAccessToken(auth_code).access_token;

        **//This is the line that i got an error because access_token is null**
        Console.WriteLine(access_token);

        Console.WriteLine("");
        Console.Read();