Mike's daily tip in Fedwiki Daily #9 newsletter 
is about embedding video.
There is a help page, About Video Plugin.
The currently supported video sites are, YouTube, Vimeo, Archive, TED ~~and TEDx~~. *Since being added TedX content has moved to YouTube.*
The steps to embed a video are:
the icon in address bar
* Press the + to create an empty factory * In another browser tab navigate to the video you want to embed. * Drag the icon in the address bar, see image, and drop it on the empty factory created in the first step. *while you are dragging the icon, you will need to hover over the tab for the federated wiki to make it current*
The video should now appear on the page with an caption below it. The caption will initially be *(double-click to edit caption)*.
To edit the caption, double click it and edit. The first line, may well wrap onto more lines, in the text box provides the plugin with where to find the video you are embedding. You can alter this first line to change which video is embedded.
discussion
Before the creation of the video plugin, video was included by pasting the embed code, an iframe, into a paragraph. But, it also required that the size parameters were altered for the video to fix comfortably.
This is no-long possible with the sanitization of content, which started with the removal of support for HTML in the paragraph plugin, and sanitization of HTML elsewhere.
Currently: it is possible to embed in a video plugin's caption. This is considered to be a bug.