Ok John,
You may need to delete the original soundtrack from your movie clips before importing them to wmm.
You need to get the music that you want to use edited in something like Audacity, use an mp3 or wav file. I see what the length of track in total is by looking at the time line and make it that length and fade the end over about 3 seconds.
Import the edited file into wmm as you did with the film clips or photos then drag it into the timeline, for audio you have to have it set to time line and not storyboard by clicking on the option just above the filmstrip at the start.
Then do the same with your second track and when happy with the results click on pubish the movie, either to pc or to DVD or mail or whichever option you want.
Personally I would always publish to pc at a highish quality and save the project as well then if you dont delete or move teh location of the files that you have used you can always open the movie again in wmm and make any changes you want or select another option to publish as.
I have just done this with a slide show that I made last year and reduced the quality so that I could email it you to show you what I did using wmm last year for my brother and sister in law.
Hope this clears up a few things for you, anything you think I can help with or I havent explained then ask again
Edited to add that I have just had my email returned as your inbox is full John, can you either clear some of it or give me an alternative address that can take an email with a 6mb attachment.