Close and lock the window. Get the radio, the weird wrench thing, and the assorted bolts. Once you've replaced the broken spring, take the radio upstairs and use it to lower the ladder. The allen wrench from the table will help you get the bat down from the ceiling. Don't take off yet, go downstairs.
Submarine Use the crane to stack the two weights on the platform, then pull the hook.
Extend and latch the bridge. The throttle from the Roost goes on the control console. Flip switches 4,1, and 6. Go to the engine room to activate the engine. Return to the console room and flip 1 and 3.