How to use a video
• Using a YouTube video can be confusing. You try to imitate the moves but it goes too fast. You slow down the video, but then you don't understand the movement anymore, because you don't recognize the music. Same problem when you stop the video.
• A sheet can help. A sheet doesn't move. It gives a stable overview of the piece. But how to figure out the notes?
• Use the free Snippz for YouTube to play it slowly: https://itunes.apple.com/us/app/snippz-for-youtube-search/id953725731?mt=8
• You can install the software Synthesia http://www.synthesiagame.com/ and download the midi file (linked in the description bar below the video) to use it in that sofware. You'll have the blue and green keys on your computer, and you can adjust the speed.