First draw a half circle with the opening at the bottom. This will represent the top of the skull. Add cheekbones by drawing two lines starting just inside the open part of the half circle and gently curving outside the circle. Continue the cheekbone line so they move downward and curve inward toward the center of the skull. Then connect the two lines horizontally. This will be the bottom row of teeth. Next draw a broad U shape connecting the bottom of the cheek bones and going across the bottom jaw line. This will be the top row of teeth. The skull has three basic sections. Draw a second U shaped line parallel and below the first and draw short straight lines on both sides. Create teeth with short vertical lines inside the smile. Slightly darken teeth faces. Add wide round eye cavities centered between the top of the head and chin. Add two teardrop shapes between the cheek bones and above the teeth for the nose cavity. Next shade everything you just drew.
If you couldn’t draw this or it was too complicated for you and turned out terrible then you can also watch this video which I do not own: