Record it, or just use the Combat Arm's youtube feature for it being more simple, won't be as in good shape though. Upload it to Youtube, or any video uploading site you know. Youtube is highly recommended. For Youtube, copy the link and paste it, you don't have to do anything else, just paste it. It should work.
Download a program called fraps, I believe there is a cracked version somewhere on this site. Use the search feature on the top of the page to find it. Once you have recorded your video on fraps it should save a file in the fraps folder, or wherever you chose to extract it. Than simply upload the file to youtube. If you need any further help pm me