1 Every time you you download a plug-in, it usually comes in a Zipped format. Zip is native in Windows XP, otherwise you'll have to download Winzip or 7zip.
(Note: Not all plug-ins comes in Zip format, some are self-install)
Now, extract the downloaded plug-in to your Paint Shop Pro Plug-ins folder.
To verify your Plug-ins folder location, open your Paint Shop Pro program, click on File > Preferences > File Locations > Plug-ins
Screenshot for Paint Shop Pro 9 Plug-ins File Location
Default Paint Shop Pro plug-in folders location is as follows:
Paint Shop Pro 6 C:\Program Files\Paint Shop Pro 6\Plugins
Paint Shop Pro 7 C:\Program Files\Jasc Software Inc\Paint Shop Pro 7\Plugins
Paint Shop Pro 8 C:\Program Files\Jasc Software Inc\Paint Shop Pro 8\Plugins
Paint Shop Pro 9 C:\Program Files\Jasc Software Inc\Paint Shop Pro 9\PlugIns