Player 2: Do the same but for the left-hand side.
Player 1 or 2: Pick up the Displacement Cube and align the laser beam so it's powering up the beacons in a straight line, opening up the exit to the second part.
Player 2: Immediately run to the ground switch on your left and stand on it so the barricade in front drops down.
Player 1: Take aim with the Cube and use the beam to fire through the glass and hit the turrets, setting them all on fire before setting it down so it's facing into the white wall straight ahead.
Player 2: Jump over the beam and place your entrance portal where the beam hits the wall, then turn around and fire it so the white wall panel here (causing it to pass through the beacon).