Hi there, this really does belong in the Site + Forum Help section of the forum, I'll move it over there for you. c:
As for your problem, all you have to do is when you're on the youtube page for your video, copy the URL and paste it onto your thread. Make sure it doesn't have 'https//' at the beginning though otherwise it won't work.
Let's take your video for example, simply put the link like this:
http://www.youtube.com/watch?feature=player_embedded&v=EIkxP03oO90
And it should appear like this:
http://www.youtube.com/watch?feature=player_embedded&v=EIkxP03oO90 (http://www.youtube.com/watch?feature=player_embedded&v=EIkxP03oO90)
:3
No worries, everyone makes mistakes. :3