How do you make the shadows of objects appear bigger on the screen​

Totally depends on the nature of the light source. If the light is radiating outward from a point source than the shadow will grow proportionately as the screen is taken further away. If the light is all parallel then the shadow will not increase in size. The size of the shadow of an objects changes due to the change in a position of a source providing light to the object. One can see the size of shadow equals to that of the object when the source is exactly perpendicular to the surface of the object. Size of the shadow decreases on changing the angle and becomes a single point when the source is parallel to the object( at the time of 12 pm, the position of sun is just above of your head. So at this time a minimum size of shadow is formed.)