In two easy steps:
- Download, extract and create a directory under /usr/share/texmf-texlive/tex/latex/ if necessary. Copy the entire directory, or the single .sty file to that location. (You need to be root)
- Run “sudo mktexlsr”
From the man pages:
mktexlsr is used to generate the ls-R databases used by the kpathsea library. Kpathsea: A library for path searching.