How to add videos hosted at other sites to the media gallery (ex. youtube)
Copy the URL of the Video to be added and follow the sequence below (steps 1-5 in that order: media gallery -> videos -> add video -> paste URL -> apply)
In the next screen that appears after clicking apply, the pertinent info such as details and title should already be filled in. If not, add your own. Be sure to set the Catagory name and to change Publish Status to Yes.