See the little white diagonal wedge on top of the base plate behind the metal heel plate. See the little black tabs sticking up behind and on each side of the white wedge. When the forward pressure is correct the edge of the white wedge will line up between the small black tabs.
You have to adjust it wil the two screws at the head of the metal arms from the base plate to the heelpiece. These screws are ony accessable when the heelpiece is in the closed position.