I'm not sure why you are having trouble with this. All you needed to add was:
Offset X=12
Offset Y=36
For future reference the CO is automatically centered on the tile it's placed on. The offsets tell it how many pixels to move from that location. A positive X offset will move it to the right, and positive Y offset will move it downward.
Now this is just bonus advice, but if you want to make the shift to the screen with the CO seamless you should copy the previous screen's appearance exactly with the static block on the ceiling. Then, add the background into your CO (see image.) This will prevent the noticeable object flash you can see when shifting between screens.
Edit: I had to edit the image a bit. I removed the alpha channel since it didn't need one. (Reduced the file size by a third.) I didn't realize the image used actual black, so the cracks and borders became invisible in game. :oops: