To do this in the application you Go To > Street Gazetteer Manager > Data > Organisation and District. When the form open, put it in query mode and query back your Organisation number. Then once it returns this, at the bottom of the form click, Produce OD XML file.
Another Internet page will load and depending on the IE version you use, you may need to right click and choose View Source (if the XML produce is all on one line) When you click view source it will load it per line.
The easiest thing to do is copy and paste this into Text Pad or Note pad and then save this as a .XML extension file.