C# Example

using System;
using System.Text;
using System.IO;
using System.Net;

namespace ConsoleApplication1
{
    class Program
    {
        static void Main(string[] args)
        {
            // You should not need this in production.
            ServicePointManager.ServerCertificateValidationCallback += (sender, cert, chain, sslPolicyErrors) => true;

            string url = "https://test.factorsnetwork.com/api/creditors/e6bcd036-2752-d00d-dd22-869ffac113be/data/2013-08.json";
            string username = "apiuser";
            string password = "test";
            //string file = "C:\\Users\\testuser\\Desktop\\08_2013.csv";
            string file = "08_2013.csv";

            // We want to force BASIC authentication on the request
            string authInfo = username + ":" + password;
            authInfo = Convert.ToBase64String(Encoding.Default.GetBytes(authInfo));

            using (WebClient client = new WebClient())
            {
                client.Headers.Add("Authorization", "Basic " + authInfo);
                byte[] data = client.UploadFile(url, "POST", file);
                string response = Encoding.UTF8.GetString(data);
                Console.WriteLine(response);
            }

            System.Console.WriteLine("Press any key to exit.");
            System.Console.ReadKey();

        }
    }
}