Cut a viewing hole in the side of the box near the
paper, then put a piece of white paper inside the end of the box near the
viewing portal.
Point the end of the box with the pinhole at the sun
so that you see a round image on the paper at the other end. If you are
having trouble pointing, look at the shadow of the box on the ground. Move
the box so that the shadow looks like the end of the box (so the sides
are not casting a shadow). The round spot of light you see on the paper
is a pinhole image of the sun. Do
not look through the pinhole at the sun! Look
only at the image on the paper.