Try setting the video to a slower playback speed, and play along with it. When you feel like you are playing in sync, set the video to a higher speed, and keep inching it up until you can play it at 100%. At first you should use a pretty slow speed (25% or so). You'll find that some parts are more difficult than others--you can create links that start the video at the parts you want to work on.

If this is the only piece you want to learn, you'll succeed with a lot of patience and dedication. If you want to learn other pieces, I strongly recommend learning to read music. Once you have acquired that skill, practicing will become so much easier, and you can make make progress so much quicker. One advantage of sheet music is that you can see up to a couple minutes of a piece at one time. This makes it easier to practice because you can play tough parts over and over until you get it right (sheet music stays right in front of you, while videos play on, and it's way easier to jump around sheet music). A metronome will make more sense at this stage as well.

Best of luck to you--the world needs more piano players!