Installing the SWS Extension (for end users)

Make sure you download the correct architecture matching your REAPER version (32/64 bit, ARM etc.).

Linux

Extract the archive in your REAPER resource folder (Options > Show REAPER resource path in explorer/finder).
That's ~/.config/REAPER for a non-portable install.
tar -xf sws-2.12.1.3-Linux-aarch64.tar.xz -C ~/.config/REAPER

macOS

See here.
Since the SWS Extension is not codesigned and not notarized, for macOS 10.15+ you can unquarantine it by running this from Terminal.app: Darwin-x86_64:
xattr -d com.apple.quarantine ~/Library/Application\ Support/REAPER/UserPlugins/reaper_sws_extension.dylib
ARM64:
xattr -d com.apple.quarantine ~/Library/Application\ Support/REAPER/UserPlugins/reaper_sws-arm64.dylib
``

Windows

Launch the SWS Extension installer and choose your REAPER install directory.