I don't think you can use a Kinect with Madden 12. Anyways, to kick you need to be close enough to the goal post on 4th or get a touchdown. To kick, choose your Special Teams (just keep scrolling through your offensive playbooks until you see Special Teams [to look at the offensive playbooks, you need to have the ball]).
Choose Field Goal or PAT, or whatever it says. Pull back the right stick back and push it forward when the meter shows up after you choose the play. Keep the right stick as straight as possible. That should help.