Share 'Open Social: getting started'

I'm a little confused about the set-up. I understand I can host my opensocial gadget on my own server as an XML file? Examples here sometimes refer to the ning open social gadget directory, or your network source tree - which I have not requested yet. The Hello World example refers to using Ning hosted XML files. Is it possible to host an XML file yourself? If not how do I set up / get access to…