How to post XML file to a specified URL

I am just starting out on this process and have been doing some searching. I want to POST an XML file to a specific URL. The URL will expect my XML file to have predetermined XML code to retrieve information from its server hosted database.

The XML code is not the issue. I know how to build the XML files correctly. However how do I place my XML file as a POST at the URL?

Perhaps the XMLHTTPRequest object? Or the ServerXMLHTTPRequest object? Or the WinHTTPRequest object?

Recent Windows versions should have all three available. They're similar but have slightly different uses.