You can embed youtube videos by using the bbcode [youtube]{videoid}[youtube] (add a backslash / before the "y" in the second youtube.)
the {vidoeid} parameter is the bunch of numbers and letters at the end of the url of the video for example
http://www.youtube.com/watch?v=pJvTWmUYTII
the video id is "pJvTWmUYTII" so the final post should look like
[youtube]pJvTWmUYTII[youtube] (add a backslash / before the "y" in the second youtube.)


[youtube]pJvTWmUYTII[/youtube]