You can add embeded youtube video in interpals message or content. I will explain you step by step how to do it.
1. Select the url of the video. just copy past the address for example http://www.youtube.com/watch?v=WObWGpe1ff8&feature=related
2. Identify the youtube code. The youtube code is in red
3. here select WObWGpe1ff8
4. Then put the code
You have an option : click the youtube button
Then past the code like this
click OK and it is done