Topic merged.
The instructions can't get much simpler really. You download the installer, run it and it installs into your RCT3 game. So when you next load it, the stuff should be there.
If it ISN'T, then something has gone wrong, but you will need to have more than a basic understanding of how your computer works to fix it (the details are all there, but if you don't understand them, it's unlikely we'll be able to help any further without more precise details).