if you google a program called "handbrake" and download it
then find the clip(on youtube), and bring up the current activity box(control+ option+ A (at least on a mac))
then click the largest file(usually a few MB)
DOwnload that file to the desktop
open handbrake and open the file
it should make it into a video, follow the directions....
check the legality of it if you are using it for purposes other than private or one time educational