[Zope] How to install hotfix?

I have downloaded and unzipped the Hotfix file into the Zope directory. What do I need to do further to install this hotfix, or is this it? I have been looking for an answer on the website and also browsed through a pile of documents and READMEs but could not find anything better than: "Hotfix products are installed just as you would install any other Zope product." But how is this done? FYI: I'm running 2.5.0 now. Thanks in advance. Best regards, Anton