OK figured it where the damn steamapps folder is finally. Basically the same thing as on PC but for those who don't know:
1) Un-RAR the file (i use stuffit expander)
2) Copy all folders (model, materials, scripts, sound) to:
Macintosh HD/Users/(User)/Library/Application Support/Steam/Steam Apps/(Steam ID)/counter-strike source/cstrike/
3) Instead of replacing like you do in windows, you may need to rename the folders i.e. models 1, models 2, etc. I tried replacing and it actually completely replaces the folder not just adding to it like in windows.
4) Enjoy!