All you should have to do is unzip the archive in your modules folder (attract/modules/shadow-glow). Nothing needs to be renamed. In fact, renaming anything will probably break things!
Once that's done, in your layout, before you want to apply the drop shadow, use this line: fe.load_module("shadow-glow")
Once those things are done, you'll need to create an instance of your snap first, then apply the drop shadow, maybe something like this:
// Load module so we can instantiate DropShadow:
fe.load_module("shadow-glow")
// Create a quick and dirty background (drop shadow won't show up against black!):
local bg = fe.add_text("", 0, 0, fe.layout.width, fe.layout.height);
bg.set_rgb(127, 127, 127);
// Create our artwork and apply a drop shadow to it:
local mySnap = fe.add_artwork("snap", 0, 0, 320, 240)
local myDropShadow = DropShadow(mySnap, 50, 10, 10, 153)
// If we want something other than pure black, we can tweak the drop shadow color:
myDropShadow.set_ds_rgb(0, 0, 51);
The values in that example are arbitrary, but should give you an idea of what's going on. Let me know if that doesn't work. I assume you're using the most recent files (from the post you quoted)? The others had some flaws!
(Edited to include comments and stuff.)