very simple.

1. Find vid you want
2. Hit the "Post Reply" button
3. In the bar above the text box there is a button on the right with the YT symbol.
4. Go back to YT and at the end of the URL there will be an = with the a code behind it. Copy this, not including the =.
5. Paste this code in between the [YouTube] enter code here [YouTube]

voila!