Linking OC USBkeys to Project Magenta CDU

I just built a FMC using Hispapanels B747 FMC panel, a Sony Psone screen and Open Cockpits USBkeys card. The keys are all functioning properly in SIOC Monitor. I just don't understand how to link it to the PM CDU. In the USBkeys Manual it says to identify the window in the .ini file:

"Window = “a.txt - Notepad”
We will write in this line the name of the window where we want the key stroke to be addressed.

I don't know how to identify the name of the CDU window. I'm not sure if this is the problem or there is something else I need to do.

Jerry