Sorry, that was our mistake - we had the competition set in the wrong submission format. You don't need to submit a YouTube video, but you do need to submit the code you used to achieve your score. If it's one file, you can submit the source file; if your code is in multiple files, just put them into a Zip file before submitting.
We've fixed our error, so you can submit your code by going to http://www.cs2n.org/competitions/vex-toss-up/submission/edit
Sorry for the confusion,