I'm having difficulty in figuring out how to install the TikZ package on my mac (i just need to draw some diagrams under the environment {tikzpicture}), the file that I have downloaded (http://sourceforge.net/projects/pgf/) is not just a .sty file. There are lot of files inside the folder. Furthermore, I have only installed MacTeX.
Sorry if the question is trivial and thanks in advance.
\listfiles\documentclass{article}\usepackage{tikz}\begin{document}\end{document}
doesn't work then you've got a defective installation. I'd be tempted to remove it and try again: there are probably other issues lurking.