So I downloaded a Lightning skin for Zoey not on workshop but on another site and I'm unsure on how to install it. My add on installer is not working and says "You can't open the application 'addoninstaller' because it may be damaged or incomplete." I've tried putting it in the add on folder but it won't read because I assume it's not set up to be a workshop file. From this point, I'm clueless on what to do next. Any help is appreciated and my opperating system is a Mac if this might make things more specific. Thanks!