Lay one long 2-by-4-inch board face down on a table. Apply a layer of glue to the end of each 6-inch long board and position one board on each end of the 2-by-4-inch board to form a "U" shape.
Place two L brackets on each side of the board, pressing up against the 6-inch boards. One bracket should be at the top and the other on the bottom of each side. Screw two screws into each bracket to attach the 6-inch boards to the long 2-by-4-inch board.
Apply a layer of glue to the front side of the 2-by-4-inch board -- the side that does not have the 6-inch boards attached. Center the crown molding on the board, the press it on to the glue on the 2-by-4-inch board. Let the glue dry for several hours.
Attach the remaining long 2-by-4-inch board to the wall, just below the ceiling. Center the board above the bed. Screw the board into the studs of the wall with the drill and screws. If you do not have wall studs, use mounting hardware suitable for your walls.
Lift the crown molding-covered piece of wood up to the wood that is attached to the wall. Use the drill and screws to screw the 6-inch pieces on the side into the piece attached to the wall. You will need someone to help hold the crown against the wall while you screw it into place.
Thread the curtain panels onto the tension rod. Use as many panels as you need to create a full look. You may only need two panels for a twin bed or up to six for a king-sized bed.
Place the tension rod inside the box of the crown on the wall. The curtains will flow down the wall to the bed. You shouldn't be able to see the tension rod.