This is pretty simple but will require a bit of practice before you get it.
When you go to make a shot you press A to start the shot. A meter will fill up which increases the strength of your shot. You press A to stop the meter. Then a bar swings back down towards a green bar at the bottom of the meter. You need to press A when the bar is in the middle of the green bar to hit a perfect shot.
The game doesnt say anything when you do it right but the achievement will pop shortly after you hit your shot.