I wanted to use the picins-package in a LaTeX document. There are two ways to get to use a new LaTeX package. One way is to download and copy the LaTeX package to the folder in which your LaTeX document is in. The latex/pdflatex will find the package in your documents folder automatically. The other way is to install the package permanently such that it can be used by other documents folder as well. The procedure on Mac OS X (10.6.8) is as follows:
1. copy the *.sty file or the whole package to: /usr/local/texlive/2010/texmf-dist/tex/latex/base/ (you must be root or use sudo to copy it)
2. use the “sudo texhash” command to make the new package available
CORRECTION THANKS TO D.W.: Local packages should go into the user TeXmf tree, which is by default ~/Library/texmf (see also the MacTeX-FAQ QM.04: Where do I put my personal additions to the texmf tree?
That’s it. Short and painless. Now you can use the package with every LaTeX file you want to compile