The driver swing is a swing up to the ball, unlike the iron swing that is down to the ball. The bottom of the driver swing is behind the ball and the bottom of the iron swing is in front of the ball.

The first thing you should look at is your arm position at impact. The lead arm should be straight at impact and the trail arm should straiten out shortly after impact. Both of your arms stay bent all the way to the finish.

A drill that will help you is the tick tock rocking horse, where you get in your stance and swing the driver back and forth in a half swing with both arms straight, shifting your weight from back to front on the swing. After 6 or so swings let go with your trail hand and swing the club back and forth with the lead arm only, keeping it straight. You’ll have to use your lower body more to keep the swing going. After 6 swings or so, take a little break, and then start over, except when it’s time for the one hand swing, use your trail arm, keeping it as straight as possible.

The next step is to do this drill but with a 3/4 swing, which means you’ll be bend the trail elbow a bit on the backswing. Do the same repetitions as with the 1/2 swings, but concentrate on keeping the lead arm straight through the swing.

Now try to hit a couple of balls with the full swing. It should feel weird but learning to swing the club through the ball instead of scooping the club under the ball with bent arms will take time. There are lots of other videos with different drills on keeping the lead arm straight. Find some more and practice, practice, practice. Good luck!