Hi guys

I own a slightly dated Macbook that runs OSX and Logic Pro 7. I'm fairly new to music production, especially on Mac, and have been told that you can't install or use downloaded VST instruments if you run OSX. Is this the case? If so does anyone know if there is a way around this? (other than changing operating system ) And if I've been misinformed would somebody be able to give me some guidance on how to install them because I haven't managed to get any of mine working yet.