You set the direction and then press the shoot button (do not keep it pushed), when the kicker starts moving you release the joystick/joypad. If you don't release it immediately you miss the kick.
I chose WF as position, and they put me both as winger and striker, so versatile role. But really random how it went back and forth between the positions.
I hate that the AI fielded me at the DM position when I was an AMC. But I always used to push up to AMC, making the 4-3-3 to a 4-2-3-1. I hope they fit that shit in PES 2011.