I know this is an old conversation. But if anyone is struggling as I was to clarify:
In the Zip you will find a folder called mysim, this needs to be put in the root of your sim city my documents folder.
On windows 7 this would be something similar to this:
C:\Users\YOURNAME\Documents\SimCity 4\MySim
MySim will contain the images which you can easily change and also a single config file