Instructions
Walk into the main room of "Barnett College" and then enter "Indy's Office" on the right side of the hall. Here you will find five brown boxes stored around the interior of the room. You can reach each of these cases with one of the five characters in the room.
Switch to a female character and jump up onto the bookcase in the rear of the room to collect the first box.
Walk to the back right of the room and use explosives to blow up the glass tent. Collect the second box.
Switch to a "scholar" character and unlock the hieroglyphics in the back left of the room to retrieve the third box.
Switch to the "Sallah" character and use explosives on the metal discs on the front right of the room to collect the fourth box.
Change to the "Thugee" character and activate the "Thugee" statue in the back right of the room to collect the fifth and final box.
Drop all of the five boxes in the center of the room and follow the prompts to build a large wooden crate. Once you have made the crate, smash it to reveal and collect a key.
Take the stairs to the top floor of "Barnett College" and enter the "Artifact Room."
Use the key on the green gem in the center of the room to unlock the entrances to the three secret rooms.