You need to edit the following file contained in the .wsz skin file.
Details of what each line of that config file does can be found here..
Scroll down a bit on that page and you'll see it.
Extract the pledit.txt from the .wsz, edit it, and then add it back to the .wsz file.
A .wsz by the way is just another format of the .zip file and it should open with your usual .zip archive program, if not, simply rename the .wsz file and try again.