When 'target' appears on the screen - click on it. While your player is running, aim with your mouse and click again to shoot. If you don't make the second click, your player will only push the ball, so you can shoot from a new position.
Football is a simple game - at least it should be. This game puts you in a role of a football striker. Your teammate is about to pass the ball to you - you need to get it before opponents and score a goal.