How do I set the weapon up

Hint 1 of 7:

First you need to assemble the catapult.

Hint 2 of 7:

GET CATAPULT ARM  and then USE CATAPULT ARM WITH CATAPULT.  +2

Hint 3 of 7:

Lower the arm for firing. MOVE LEVER on left side.     +1

Hint 4 of 7:

You must be in front of the catapult to move the lever.