I did eventually manage to get one side to load a separate texture but it loaded on both faces of that side (inside the cube and outside) therefore if I look through the 'window' in the applied texture I see the back face of the opposing side. I can't seem to select the back side and set it to transparent.
What am I doing wrong? I have tried many different option settings but most of them deliver an incomplete object when I import into Kitely
If anyone has a link to a tutorial please share.

Oddly I did not have any problem individually texturing different faces of a very complex window frame construction or a curved extrusion of a crown molding once I exported them to Kitely, but I can't seem to replicate it on a simple flat wall