You are given it by the girl at the mueseum!
If your talking about Counterfeit Island then you get the key and go back to the museum on Counterfeit Island
Early Poptropica.
You use it.
The key fits the Inspector's cottage in the Countryside.
blah blah blah
skrow you
In the supply room
It will.
you get in the boat and sink
You now have a key that fits a lock on Counterfeit Island, and you haven't found a key to the lock on the Inspector's house, so...
There is no key. The chest is just a distractionnowhere it is a distraction
There is no key. Go upstairs to find the painting.