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...
well it depends on what kind of machine you are on? are you a mac or pc?