I followed the correct link and downloaded the correct version, for Mac. Then I moved the whole file into KSP's GameData file, parts, FX, and all. I then opened KSP and only the SRB's, external tank, and cargo bay were in the inventory. I then checked the CSS file and all of the parts were all there. Nothing seemed to work. Do I keep all of the CSS files, such as Parts and FX and also the simple and advanced shuttles, in the CSS file or do I have to transfer those files to another file within KSP? IDK. I have also tried deleting CSS and downloading a new one, which didn't work any better than the original try. How do I install it right?