Once you have the multi-tool from the Clockwork Cantina (big gears go at the top and bottom), throw the lever to extend the bridge to the roof. Use the hot air vents to throw you across to the right side of the roof, and open the skylight using the multi-tool.
its in the museum on mainstreet of steamworks island :)
It's Steamworks Island #14th Island
(The solution is at the related question "How do you beat Steamworks Island")
the crab on steamworks island is next to the living quarters
The mayors term of office is 50 years
You go to Steamworks and head to the museum and there is the Deogen
steamworks island
There is a video walkthrough at the related link below. There are written WikiAnswers solutions at the related questions, as there are for all Poptropica islands. (How do you beat Steamworks Island) (What is the walkthrough for Steamworks Island)
Steamworks island
you can get it on the far left of steamworks island, past the living headquarters.
how to do the bridge terminal on poptropica's steamworks island
jump