The FSM page doesn't completely help; it's lacking information.
You have to use a standard youtube link. The standard link looks like this:
youtube.com/watch?v=
And the link is completed with a series of numbers, letters, and certain symbols which identifies each video. Like this, for example:
youtube.com/watch?v=jKtsJC362nM
That's a standard youtube link. If you find yourself on a video that has tons of characters in the link and you aren't sure what the series of numbers, letters, and certain symbols are for the link, right click on the video screen and select Copy video URL.