How To Set An Object Detection Trigger and Response?

Q: How To Set An Object Detection Trigger and Response? 

I'm trying to make an appear as a response to an object being detected. In other words, the moment an object (e.g. car or book) is detected, a trigger is fired; and the response is a texture enabled. 

Typically, the trigger and response flow is configured using the behavior script. However, I'm unsure what to select as a trigger from the drop down menu, if this is actually the correct way. If it's not, can someone share an alternative method for a rookie user like me.