Your Video Card (in the 'Build Your Own' section) will support videos hosted on Vimeo, Youtube or Wistia.
Adding a video to the card is very simple:.
Just select your source, and enter the last part of the URL for the video.
For example, 'https://www.youtube.com/watch?v=rqQPAzuGxyU' would be shortened to 'rqQPAzuGxyU' and entered into the video source box:
That's all you need to do! Flip the card and you'll see your video ready to be played within your board.