Hi. I am playing RCT3 on iMac os X El Capitan. I've tried checking the play music from iTunes option in settings but i get an error message saying there is a problem communicating with iTunes. I've also tried looking for the music folder in the rct3 container but I can find the location of the preinstalled music such as mermaid.m4a. I was thinking if i found the location of those files i could add my music files to that location.

Well, you've to go to your Application folder, than right click on RCT3 App and click "show package contents". Then Contents/GameData/Music and you can find all the .m4a files