Just put the link in description.
Put the video in as many places as you can, if there is a site for sharing video, share your video.
When it comes to marketing, you just need as many eyeballs seeing your video as possible, so get it out there.
If your video would be good for a niche market, then that’s even better, aim towards that market. Also, you if you have the time, you can even edit your video to reach users on a particular site. For example, on a gaming site aim it towards gamers, on a business site aim it towards business. It takes longer, but for the sales you could accomplish without spending a penny, it’s well worth it.