How does transformation program start up?

Hi all,

I created transformation program which should in theory change incoming (from a vendor PO_ID to what we have in the system). I configured routing so it knows about my transformation program:

But for some reason my transformation program doesn't kick in. When I created AE I change the properties to transform from incoming message to the same one? Is that correct?

This is my first time with Transformation Program, and I'm not sure if I'm doing everything correctly. Please see below for the code from my app engine as well as properties from it:

/* Get the data from the AE Runtime */