polaroid d&s works either way, as a stand-alone or as a plugin. i forget how it installs if you want it as a stand-alone, but there shld be a readme on the site you got it from or within the download file somewhere. normally these install by simply double clicking the .exe file if it has one, or by double clicking a setup file. if it's zipped (having a .zip extension) you'll need to un-zip it first with a zip/un-zip program like winzip.
once you either unzip it or install it, look in the folder where you installed it or unzipped it and you shld see a file with an .8bf extension. if you want it as a plugin, simply move the .8bf file into your plugin folder with the program (psp or ps) already shut down. the next time you run ps or psp, whichever you put it in, then it shld appear available to you. i dont know where ps allows you to access them, but psp accesses plugins from the 'effects' menu.
and bingo, you shld be up and running.