To add a video to your Youtube Vimeo Video Module, hover over the gear icon and click settings. Click on the 'Video Settings' tab on the right and add the url from the youtube or vimeo website you wish to take the video from.
Make sure you take the full url from the site and not the embed code or other options. Then paste into the module and click Update.
The module automatically formats the size of the video to the dimensions of the pane the module is located.