Oh, I see you are already on the road to success.

Well, either you style the hairs, OR you drape the hairs using dynamics.

Or you do a primitive styling first, and drop the hairs from there.

To get dynamics working, you have to select the head, the neck, the collars (in the pose room, one group at the time, before running the dynamics) and put a checkmark in the collision detection boxes. That way the "falling" hair will collide with head-neck-collars.

If you do not active the collision detection on each group, the hairs fall through the head-neck-collars.