I found it extremely hard to get a penalty during the game. The CPU simply isn't aggressive enough to make it happen.
That said, there's an incredibly easy way to get this. Go into an amateur level exhibition match against a bad team, hold the ball for the entire 90 minutes, and once the final whistle blows 0-0, select penalty shoot out. You've got a few chances to score a goal, but keep in mind the meter on the bottom of the screen needs to be in the green area when you tap the area of the net you want to shoot.
I scored 2/3. Easy easy. Enjoy!