Find it: Click the Script Editor button on the Action
palette:
Use the Script Editor to build special behaviors into your scene file using scripts. A script can be routed to the incoming and outgoing events that are part of the nodes in your scene. It can also be connected to sensors that notify the script when certain things happen--for example, when the user approaches a certain spot, clicks an object, or bumps into a wall.
For information on scripting, see these pages: