There are two places you can add a YouTube video in your stories.The first is as inline media in a Text, Background Scrollmation, Scrollmation, or Reveal section. Before and after each text block you'll see a menu bar that enables the addition of several different objects to the column:Click the puzzle-piece icon labelled "INSERT RICH EMBED" and a window labelled "Inline Media" will open, with a toggle set to the "Rich Embed" option: Paste the URL of the YouTube video you wish to include into the input box labelled "PASTE A LINK BELOW", and a preview of the video will appear:A caption that will display under the video can optionally be added.  Then it's as simple as clicking the "SAVE CHANGES" button, after which the panel will close and you'll see the video in context with the rest of your story:In Media sections:A Media section provides the opportunity to show a larger version of the video.  Once you've added this section to your story, you'll see the default image of a bird. Select the green media icon on the left hand side of the image:A media panel will open, and by default it will be set to insert an image.  Click the option at the top of the panel labelled "Rich Embed:The panel will change to provide an input box into which you can paste the URL of the YouTube video you wish to include (the panel also supports a wide range of other media types):After pasting in the URL of the YouTube video, the panel will show a preview of it:If you wish, enter a caption for the video, then click "SAVE CHANGES".  The panel will close, and the video will be shown in place in the Media section of your story.You can read more about Rich embeds here.