Step 1 - Orientation
As shown above, your folded Lightbox should be orientated so that the thicker of the two halves are on top.
Step 2 - Unfolding
Insert both hands as shown in the picture, palms facing upward. Again, make sure the thicker of the two halves is on top. Adjust your fingers. You should only feel the top two plastic side flaps.
Press down with your thumbs. Use your fingers to pull away the inner two flaps. As shown above, once unfolded, be sure to re-orient, so that the light strip is positioned on top.
Step 3 - Assembling
As shown above, the bottom wing flap should be positioned between the top and bottom wing flaps, with top-most wing flap on the inside.