Where can I find the download for iScreensaver 5.2.2?

All I see is version 6, and I wanted to use the older version.

It’s still available, just at the very bottom of the Downloads page.
See https://iscreensaver.com/downloads.shtml#legacy

Please note that version 5 is quite obsolete, and will not work with macOS 10.13 or higher.

Version 6 actually works better with all versions of macOS, as it can build screensavers that work with old macOS 10.11 up to the very newest macOS 11 Monterey (which is in beta testing).

Version 6 is also better on Windows, as it makes a compact single-file installer EXE and SCR, which is a lot easier to deal with.

We strongly recommend you upgrade to version 6.