t-20-07

Hey. So I'm trying to install 'The Return Of Dr. Sloth Decoder' program since decoding the puzzle by hand takes forever (for modifier 3).
Also, I realize I need some required files in order to download from this site? I wasn't sure which of the 'required files' I had to download. I found three, but don't know which are actually needed.
Also, I don't know if I have to "save" or "run" everytime I try to install, I don't know where to unzip them to, I don't know what to do after I unzip them.
Could someone please guide me step-by-step?? =[