ConnectionOptions without username and password

I get access denied error when I'm trying to connect to a remote cluster using the below code. I wanted to establish connection without supplying username/password in the code. I stored them in Windows Credential Manager. This works when I provide username and password in the code. How should I make it to read from the credentials manager?

                ConnectionOptions Options = new ConnectionOptions();
                //String Domain = "mydomain";
                String Domain = "";
                //Options.Username = "administrator";
                //Options.Password = "mypassword";
                Options.Authority = "ntlmdomain:" + Domain;
                Options.Authentication = AuthenticationLevel.PacketPrivacy;
                ManagementScope Scope = new ManagementScope(@"\\win2012cluster\root\cimv2", Options);
                Scope.Connect();