Type "%appdata%" in Windows Explorer (without quotes), and go to "vlc", then proceed to "lua" and finally "extensions".
If any of the folders doesn't exist, create the missing folder.
Paste the "vlcsub.lua" file in the "extensions" folder.
Now, open some file with VLC, and go to "View -> VLSub".
It will open a dialog where you choose your language. Select your language, and press OK. It will start searching for subtitles from "www.opensubtitles.org". Choose the one which you find most suitable, and press OK. The subtitle will be downloaded, extracted, and loaded in VLC.
I successfully edited the script, and now it's working flawlessly.