ok this is how i do it. you need to download the video from youtube first. google download youtube videos. thats too easy.
next, you want to find a video converter. need to be able to convert the video to a .mov file. you can google that shit and there is a site that does it online... so u dont have to download any software.
once its converted to .mov file... i the use photoshop. import the .mov file into photoshop and trim the frames down to about 140 frames. save as optimized and there you go...