Cool! Is the video embedded in Facebook from another site like YouTube? What I'd do is go to the source of the video and copy the URL for the page on the source site with the video on it. Then when you post on UU, click on the video link at the top of the box into which you type your post (it looks like a film image with two film frames). Paste the URL into the dialog box that comes up when you click on the film link, and hit okay, and hit the Post quick reply" box.
It's best to post the video in the "Video and Links" forum.