I do have the disc, but since I have windows 10, I do not see Atari or a "themed" folder in RCT3 Documents, so I can put the downloaded material in there.  Is there anything else I could possibly do?

---

Also, I do have both expansions Soaked and Wild.

c>program files (x86)>atari>rct3 platinum> and theres all the folders to put custom stuff

^Yeah, that's pretty much the best explanation of it

Thanks! I just found it.