I'm new on this forum and to LaTeX, so please excuse any silly questions

I've been searching now for 2 hours on how to do this, and it appears I need some assistance...
I'm trying to use install a .bst file (bibtex style) and to make citations and reference list in Texshop. I'm using OS X btw.
When I'm using any of the bibtex styles that are preinstalled (like plain or apalike) my references show perfectly. I would however like to use another (called apa.bst), but I can not get it work.
my latex test file looks like this:
\documentclass[12pt]{report}
\begin{document}
citation test \cite{Andersen:1783zr}.
\bibliographystyle{apa}
\bibliography{test}
\end{document}
I hope you guys can give me some input on how to solve this! Thanks alot!
R