FOP error-- am I doing this right?

I have fop 0.20.5 installed on SuSE 8.2, and I have managed to set JAVA_HOME correctly.  I'm using the Sun j2re 1.4.2. 

But when I run any fop command, even just fop --help, I get this error: 

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/fop/apps/Fop

Am I doing this right?

I've used xsltproc and the docbook-xsl-stylesheets to generate FO output, and the FO file seems fine. How do I get from FO to, as it were, FUM (that is, PDF). 

(ha. ha. Jack & the beanstalk. Get it?)