How to add a node in an xml file lacated at a server (not locally)

Hello all!!!
I'm using the below code to add a node in an xml which is located in my pc.
            XmlDocument doc = new XmlDocument();
            doc.Load("names.xml");
            XmlNode name = doc.CreateElement("Name");
            XmlNode username = doc.CreateElement("username");
            username.InnerText = "25061";
            XmlNode paid = doc.CreateElement("paid");
            paid.InnerText = "No";
            name.AppendChild(username);
        ...