http://www.youtube.com/watch?v=pRpeEdMmmQ0
Let`s say you want this video.
All you have to do is to copy the part after the "/watch?" thing in the link :
http://www.youtube.com/watch?v=pRpeEdMmmQ0
Then you replace the "=" in the link with a "/" :
Before replacing : v=pRpeEdMmmQ0
After replacing : v/pRpeEdMmmQ0
Here`s the last step : You have to surround the replaced thing with a YOUTUBE-Tag, like this :
v/pRpeEdMmmQ0
The upper code will generate this :
v/pRpeEdMmmQ0
After you`ve done this with your video I`ll explain to you how to paste the youtube video right next to your name (only visible on your profile) if you want.