Make your edit.
On the toolbar that WMM gives you, 3) is called "Finish Movie." Go to that list, and click the first option, "Save to my computer."
Go through the steps and do it up, it's basically like exporting. Sometimes it can take a longgggg ass time, depending on how fast your computer is, because WMM blows.
Good luck mang. Post again with any questions and I can try to help you out more.