first download fop, for example : http://apache.root.lu/xmlgraphics/fop/binaries/fop-0.20.5-bin.zip

extract the zip in the following directory :
C:\Program Files\Altova\FOP

then in XMLSpy, you go in Tools menu>options>XSL, and at the bottom, you will see "please enter path to XSL-FO transformation engine (if using FOP enter path to fop.bat), and you enter :

C:\Program Files\Altova\FOP\fop.bat

that's it

2006/11/17, Alpa Chadha <alpachadha@gmail.com>:
I am working in XML spy.how can i set the jar files of fop in XMl spy..
I want to run my XML:formating objects application in xml spy
kindly reply me as soon as possible.