How do I install packages on macTeX?
Answer
If you get a "file was not found" error for a class file or package, it needs manually installed. Most class and package files are at ctan.org.
If you've never manually installed packages using macTeX, create a texmf folder in your Library folder. In texmf, create a tex and a bibtex folder. Create a latex folder in the tex folder and a bst folder in the bibtex folder. Install the bst files in the bibtex/bst folder. All of the other files that are not documentation files or tex files are installed in the tex/latex folder. Usually, I create a folder for the package in these folders to be more organized.
There is an installing packages webpage on the LaTeX library subject guide that has a demonstration video on macTeX.