First, navigate to the YouTube Video you want to embed on your site.

Click Share

Click Embed (you can also simply copy the Share link and copy the url into the Video content on your webpage.  Embedding gives you some more options though, including eliminating the suggested videos screen when the video ends.

Click Show More

Deselect Show suggested videos... to prevent YouTube from suggesting videos after the current video is complete.  (Content can sometimes exceed PG rating.)

Copy the html code.

Navigate to your Streamline sandbox and click Edit this content  on the page you want to embed the video

Click +

Select HTML and past the HTML code in this box

Click Save and close

Your video is embedded on your site! That's it.  You're done.