After running the installer, you can delete the two new icons on your desktop, they're useless. Go to Final Fantasy VII folder and find the data folder and look around for ffprp. In the folder, change the 00.lgp to char.lgp and 01.lgp to world_us.lgp. Replace the existing char.lgp with the new one in the field folder and replace the world_us.lgp with the new one in the WMRP folder. Both the folders can also be found in the data folder. Once you are done, delete ffprp and run the game.
You should now have some new pretty awesome sprites!