If you are submitting a video already on your channel, if it's accepted, you must set the video as unlisted through the "video manager" section of YouTube. This is to avoid YouTube punishing both videos in searches due to repeat videos. If you have a video not uploaded to YouTube then you should upload it, set it as unlisted, then provide a link. One of the YouTube staff will then use a Video downloaded such as http://keepvid.com to download it then upload it to the forum channel. Videos should be in HD preferably as well - if you need help rendering clips contact Total Mayh3m or Mr. Biggles who can put it in contact with people with HD PVRs.
Just my two cents from when I used to run the channel.