I found a script on this site which adds the filename to my image. However it is NOT an Adobe JavaScipt file but rather a JScript Script File.
Are you sure its not a Photoshop Script. If you found it on this site it is most likely a Photoshop Script. Photoshop script have a file extension of .js or .jsx many .js Photoshop Scripts can be renamed to .jsx and still work. Years ago there were only .js files then Adobe came up with .jsx for files that only use Photoshop supported function. Photoshop Scripts can be run from any folder on one's machine. I keep mine in "C:\Program Files\Adobe\Adobe Photoshop Scripts\My Scripts" and I place a shortcut link to "C:\Program Files\Adobe\Adobe Photoshop Scripts\" into My currently installed versions of Photoshop folder "Photoshop version\presets\script" All installed versions of Photoshop get my scripts from a single location which stays put and doesn't move with each version of Photoshop. This is very important for I use many of my scripts in Photoshop Actions. If a script's locations changes with each Photoshop release the actions that use them would need to be recorded for each version of Photoshop and kept in a location for that version of Photoshop. I prefer to keep one copy of my actions in a single location that does not move. But of course these have to be loaded into each version of Photoshop. Still you better off keeping extensions you add to Photoshop outside of an Adobe folder. "C:\Program Files\Adobe\Adobe Photoshop Scripts\" is my creation not Adobe's. However not all thing can be install outside of Adobe's folders some third party developers foolishly hard code in them code the require themselves to be in Adobe's tree.
You may also want to open the ESTK (ExtendScript Toolkit) should be installed on your machine somewhere (utilities folder on the mac). Then navigate to your script.js file and try to open it. The author of the script in question may have put some commented notes on its usage in there etc… Might give us a better idea of the scripts content… and how best to use it…
Make a Folder in your C drive and Name it PS Scripts.
Open Note Pad and copy the scipt into Note Pad. Now, and this is important change the Text Document on the lower right corner to All Files.
For File Name type the Name toy want to give to the script and right after it .js (dot js) no spaces and save it to the folder you just made.
Invoke the script from File--Scripts=Brows to the folder and the script.
I put my scripts into the C drive for the same reason JJMack does.