I've added a "reveal all" mask, as indicated by the white rectangle to the right of the thumbnail in the top layer. With a "reveal all" mask, ALL of the contents of the top layer are visible. To hide or erase the contents of this layer, we will use the BLACK paint brush. Everywhere we paint with black on this layer, the sharpening will be hidden. So let's get started painting over the areas that we don't want sharpened.