Save file in a shared folder not in network or outside network in C#

Question

Hi,

 We have a cloud based apllication, there is a facility called image upload where user can select an image file from his local drive and save that file to a shared folder which is not in user's network. The code with I have written works for shared folder in network but outside the network it fails. 

              Currently I am passing path which has IP address of shared folder's computer and shared folder name attached to IP address. I think I need to pass username and password also with IP address.

 What I have done is

string FileName ="Image1.jpg";
string Root = @"" + "IPAddress\\SharedFolderName" + '\\' + CustID;

 if (!Directory.Exists(Root))
                   {
                       Directory.CreateDirectory(Root);
                   }

string filePath = Root + "\\" + FileName;

File.WriteAllBytes(filePath, Convert.FromBase64String(image));
\\ Here "image" is file content which I want to save in shared folder.

 This code is running for shared folder in network. But to access folder in other network I  think I have to pass username and password.

How to do that in c#?

Any help would be appreciated. Thank you.