Unzip using either pkunzip or unzip as follows:
unzip os2www.zip OR pkunzip -d os2www.zip
OR
pkunzip -d os2www.zip
Shut down the existing PowerWeb server.
Restart the PowerWeb server, by running the "PowerWeb" batch file in your server root directory.
If you subsequently need to revert to an old version, there is a menu option on the main "/admin" page to choose which version to run.