To install you should extract all files into addons folder.
I don't have a list for all galaxies in the mod) You may get the idea by looking at the files of the mod.
Currently that is impossible. I tried making NGC 660 but SE is too limited for that now.Oh yeah! I want that one to! That and NGC 6621/NGC 6622 if that's not to much to ask for.Can someone try to make this Galaxy ?https://en.wikipedia.org/wiki/NGC_660