You would need to use the embed code from youtube and paste that into source code view of the content area.
for example, if you look at our content management you tube tutorial:
and go to the embed link, it gives the following code:
<iframe width="560" height="315" src="//www.youtube.com/embed/tGUP3-BnVfU" frameborder="0" allowfullscreen></iframe>
you could add that video to your content area by pasting that code.