How do I make Youtube video of my score appear in the score's description?

I see a lot of people doing that and I'd like to do it too. Also just to make sure, can the video be unlisted?

you need to use this tag

[youtube id: xxxxxxxxx]
(no space between id: and x)
and yes you can use an unlisted video

your videos "id" can be found in the address bar
this picture is an example