Adding video is extremely easy. Just copy that Share link from YouTube and paste it to the place you want your video to appear. That's it.
This method makes your video to take the whole width your website page. If you would like to re-size it add the following construction to your page:
[embed width="480" height="360"]Your video URL[/embed]
Replace 480 with desired width, 360 with desired height, Your video URL with the URL from Share link on YouTube. You may define either only width or only height and the website will automatically calculate the other.