Ok, as you can see, this drill requires constant kicking and a lot of core body strength. Keep your hands at your side, like you have them in your front pockets (don't move them). Your eyes are looking at the bottom of the pool or at the sky (not to your sides like in the video). Your body rotates on an axis that goes through the top of your head and comes out of your toes. The swimmer in this video does a good job of rotating, however, he is a bit too jerky. The rotation should be very smooth, trying to minimize the visual effect of tightening your muscles to turn. Also, it is nice to turn on your back, however, I'd keep the rotation only from one side to the other across your front, so you never end up with your belly up. Start on your side, looking down, then rotate to your belly, head still down, then rotate to your other side and now you can rotate your head to breath in the same axis as described above.