Apply for the job with the assistant curator and when you pass the Forgery Detection class, he will give you a key to the Supply Room.
The same way you got in to get the picture piece : use your key.
Get the paper
In the supply room
the supply room is in the mussem on the first floor to your far left
After the museum closes, you go in the underground tunnel with the torn picture and match up the picture with the exit vault picture. The exit leads right into the supply room and from there you can access the security room.
Once you have passed the Forgery Training, you will receive a key to the Supply Room. You have to use it to get the Dragon Face picture piece in the room, so that you can complete the picture and enter the museum at night.
Collect the six pieces of the dragon picture, and rearrange the features on the dragon face lock. This opens the trap door into the Supply Room. (see related question)
Don't ask me, o_o.
you get them when you get a job there. Talk to the assistant curator
finish the tests and he will give u a key.
The inspector is not around to see the "dragon picture", because you get the last piece in the Supply Room. She does see the "thief" picture when you print it from the video surveillance tapes. But she says she doesn't recognize him.
It is for to unlock the door when you go under ground for this undrer ground tunel tour the door with the dragon face leads to the supply room in the Museum.