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)
Get the paper
In the supply room
the supply room is in the mussem on the first floor to your far left
you get them when you get a job there. Talk to the assistant curator
finish the tests and he will give u a key.
Don't ask me, o_o.
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.
Once you pass the test by the assistant curator, and finish the Forgery training, he will give you a key to the Supply Room.
The same way you got in to get the picture piece : use your key.
You get it when you pass the Forgery Detection training with the assistant curator.
you can with the key!
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.