I've installed your plugin according to official GIMP help http://registry.gimp.org/node/25574
I'm reopening the GIMP but I'm unaware where should I search for the plug-in.
Is it in Filters? Should it be under Filters-> Noise?
P.S. Which file should I download:
c) may be both
d) None of above, the file is elsewhere.
Thank you for pointing out the GIMP Help | Gimp Plugin Registry page:
It has the link to this excellent blog on "How to install scripts & plug-ins to GIMP (Beginners)"
It covers the major OS's and I wish I had known/found it earlier :)
It also provides a way to determine where to determine where to expect the plug in to appear, i.e in this case "Filters > Noise".
You may install both plug-ins, noise-generator does include a Poisson noise option, so you might only want to install that. No harm installing one or the other or both. You would see noise-generator plug in as "Filters > Noise > Noise generator..."
Hopefully this helps you -- if not, please post more details, provide your operating system (Windows, Mac, Linux variant) and the version of GIMP you are using.