It's ok took me a while to learn how as well:P Well, when you download a file first extract as you would any other file for custom scenery. Then open up the folder and there should be a readme. Some don't have any though The next folder that you see should be copied and then placed inside Atari/Roller Coaster Tycoon 3/Style/Custom. If you do not have a folder named custom you can simply make a new folder than title it custom. It is just like installing custom scenery but instead of going into style/themed it goes into style/custom.