The key card will open the door in the Black Widow's lair, once you get past the guards.
(see related question)
it is in the statue room
you go to early poptropica, and go inside the gray art place. there you talk to the lady in purple and get a key. the key goes to the locked house back in counterfeit island.
Get the paper
Find out for yourself
In the supply room
In the Statue Room.
In the upper left of the museum.
You don't, because there is no key. The chest is just a distraction.
in the lighted room on the second floor
it is located in the black widows lair
the supply room is in the mussem on the first floor to your far left
It takes you back to the hallway that you came in through the locked door.