There is not a good central repository for KiCAD parts, and on the client side the process for managing components or creating new ones is very convoluted. KiCAD is tremendously useful, but its creators need to take a serious look at usability. A cloud-based parts library would be a killer feature, along with drop-in public domain circuit "modules" (comprised of several to many connected components).
As Sam mentioned about, this is definitely something they'll be working on. If you use some of these parts and have a known working footprint, I'm sure they'd appreciate your help.
This is the most promising installer at this point but it's still not very usable: http://discuss.wayneandlayne.com/t/new-os-x-builder/73/18
Gotta say, there are lots of Kicad dmgs out there, but I have yet to see one actually work well. I'm not sure I've even seen one described as working well by the person posting it.
As Sam mentioned about, this is definitely something they'll be working on. If you use some of these parts and have a known working footprint, I'm sure they'd appreciate your help.