using System.Net;
HttpWebRequest Imgrequest = (HttpWebRequest)WebRequest.Create("web address");
NetworkCredential credential = new NetworkCredential("username", "password", "domain");
Imgrequest.Credentials = credential;
HttpWebResponse webresponse = (HttpWebResponse)await Imgrequest.GetResponseAsync();
var stream = webresponse.GetResponseStream();
Thanks,
Bilaal