Cut the particle board for the size you want your screen to be.
Cut the blackout cloth to be the same size as the particle board, with about 4 inches extra on each side.
Cover the particle board with the blackout cloth. Stretch the cloth tightly over the board, and fold the extra cloth over to the back side of the board.
Using the staple gun, staple the cloth on the back of the particle board. Make sure to keep the cloth pulled tight to avoid wrinkles.
Use the nail gun to mount the screen on your wall. Put a nail in each corner, as well as in the top and bottom. If it seems unstable, add nails to the sides.