Here is a little drill you can try on the practice ground to help you get the feeling of starting your downswing using the ground as leverage.
Place a golf ball on the ground and press the ball into the ground a little to prevent it rolling around.
Now take your set-up with the golf ball under the middle of your left foot, if you’re a right handed golfer. I would not recommend you try and hit a ball with the ball under your foot, as may put a bit too much pressure around the ankle.
Make a ¾ back-swing, pause slightly and start the downswing by trying to push the ball down into the turf.
Once you have the feeling of pushing down into the ground momentarily at the start of your downswing, remove the ball from under your foot and try hitting a few shots with this feeling.
Advanced PGA Professional Paul Thompson, November 2012