You are getting some great advice from TomB, Kneale, and dchan. I will agree with all they have been saying!
On the older(read" straight") skis, we had to lever forward and back fairly actively, to get the ski to do what we wanted. The idea of "pressuring" the front of the boot was also a means which many instructors used to get students not to sit back(kinesthetic awareness).
Enter shape skis. Softer, wider, shorter, etc. We no longer need the strong leveraging aspect. But steady contact between the shin and the tongue of the boot remains as a positive thing!
Now- for the rest of the story.....
Many skiers think that because we've(instructors) asked them to feel that contact, that it also means to be pressuring downward under the ball of the foot.
Appropriate stacking of the body requires that we be standing where the leg attaches to the foot. I've yet to see anybody whose leg attaches in the front half of the foot!!!
So- get used to the feeling of pressing down through the back half of the foot, while maintaining contact with the shin/tongue. This aligns the body more naturally, allowing the leg to effect stronger edge control, and directional control. All of this provides greater balance, and manueuverability.
Good luck, and don't get frustrated!