Adding new file to an existing sample

Hello,

I watched the tutorial and have used other scripting languages in the past.   What I don't understand is how SceneGraph knows about the file I'm adding to a working example.  

Here's what I have, in the samples I want to use postergrid.xml and include it into Roku Recommends and then call the function "showpostergrid()" from within MainScene.brs.  I get no errors, nor do I get an grids appearing as expected.  

How do I test if the postergrid.xml is even being recognized and the function being called by the main program.  

I apologize in advance if this is obvious.  I've never used this platform.  I would really appreciate if someone could shed some light on this issue.  Thanks