The easiest way to do a slideshow is by using Windows Movie Maker. Just open it, import the pics you want along with the music and drag the stuff down to the timeline.
If you mess around with it awhile you'll find transitions you can drag into it, adjust the length of time for each pic, add text, all sorts of stuff. Just pay attention to where the song ends on the timeline thing and have enough pics to fill the time.
After you've saved it to your computer it'll be a .wmv video file which you can upload to Youtube.