Not sure where you can upload it to.. well I do but I only know of like, Rapidshare, Megaupload and sites like that.
You use Fraps to record the demo player. Basically, you start playing the demo and press whatever button you bind to turn on recording from Frap. Once done, press the same button to stop recording. It's real simple once you have Fraps. Then you upload the video to YouTube. Though, if you record at high FPS (in Fraps), the composed video will be a lot of gigs.