The file you download is called 'tsljeditemple.rar' so you need to download and install a program like 7zip (free)
or WinRAR (trial)
and use it in order to open tsljeditemple.rar. It's basically like a .zip file, so plonking it here or there won't do the trick.
Inside the .rar folder is a series of other files, including Install.exe. Extract ALL of the files to either a new folder or somewhere that you'll remember the location, and make sure any conflicts are overwritten.
Once that is done, when you run the Install.exe (double click), click 'Install Mod' and follow the instructions.