Instructions to submit your video, from the SFM site:
The full rules can be found here.First, upload your video to YouTube, with privacy set to public, embedding enabled, and advertisements disabled.
Then, navigate to your videos page on Steam Community.
If you haven't recently linked your YouTube account and Steam profile, you'll see a Link YouTube Account button at the top of your Videos page. Click that button, click the Access your YouTube videos button on the next page, and log into YouTube.
If you have recently linked accounts, you'll see an Add Videos from YouTube button at the top of your Videos page - click that button.
Select the Video you want to upload from the list of your YouTube videos, then under Associate the video(s) with a game, choose 5th Annual Saxxy Awards. Then click the Add Video button.
Voting opens on Wednesday, November 11 as soon as the submission window closes. You'll be able to vote here.
I'm submitting to the "Short" category this year with this. YouTube version is here: