Adding a (Youtube) video is as easy as finding the ID, and making a call like this:

{% include widgets/youtube_embed.html video_id="Ll5hBN6Dh5M" %}

The result will look like this:

More text

Remember that this is just a post, so you can add whatever text/photos/etc you want to this item. You can even embed another video. In the call below, I specify the width and height, which are both optional: