Position the Scorer around the edge of the penalty box. He should be relatively alone. Once the Scorer is in place, run away from the goal with a Passer. (You must have the ball.)
Press the "Pass " button to make the Passer send a long ball to the Scorer. You can slightly overhit the ball to reach the appropriate height for a bicycle kick.
When the ball is in the air, move the Scorer one step forward toward the Passer. The Scorer's back must face the Goalie and the soccer ball should arrive at the Scorer's chest.
When the ball is an arm's length away and at chest height, press only the "Shoot" button to make the Scorer perform a bicycle kick. I've also performed this trick by pressing the "Finesse shot" and "Shoot" buttons at the same time.