[Zope] Third Party Products

How does one install third party python products such as PIL or ReportLab so that Zope's python interpreter can find it in it's path. I have installed both of these python products on a machine that has python installed and not Zope and I have no problem using them. I am trying to install them on my Zope machine so that I can using them in my Zope site, but I can't seem to get Zope's python interpreter to find them. Should I install them in the Extensions directory or where? How does one set the Zope python path? Or is the evaluator stuck half way up. Thanks, Dan