Note: these instructions are somewhat out of date as of January 31, 2003.
To download a .tex file on a Macintosh, hold down the Control key while clicking the link, then select Download link to disk. Save it in a new folder, maybe on the desktop.
Launch the editor Alpha by clicking the apple in the upper left corner, Applications, Alpha. Pull down File, Open, and open a .tex file. To process with OzTeX, pull down the menu headed by the bearded OzTeX lion and select Typeset filename.tex. This launches OzTeX, which begins processing the LaTeX source file. If there are mistakes, OzTeX gives some indication where the mistake is (by line number) and what sort of mistake it thinks was made. If you want it to stop telling you about mistakes, respond with the letter x, then enter. Once you have worked out all the mistakes, OzTeX will finish typesetting the file with no complaints. Now pull down the View menu and select View filename.dvi. A dialog box appears. I recommend checking the box Make missing PK fonts, since that will work out the necessary information to display such things as the small capitals font and the math symbols when you use the amstex package.
Click on homework.tex, which is a short example of a LaTeX document. Internet Explorer will not recognize what type of file it is (what MIME type), so it will prompt you to save it to the disk. I would recommend saving it on your desktop in a folder called latex. Make sure to save it with the .tex extension. Now start the LaTeX editor AlphaLite (you may need to search for AlphaLite using Sherlock). AlphaLite colors commands and comments, making it easier to see what's going on in the LaTeX source.
You can run latex directly from AlphaLite by pulling down the icon saying LATEX, then directing it to the location of OzTeX: Desktop, Macintosh HD, Applications Folder, OzTeX, OzTeX. You only need to do this once per session. Once OzTeX has processed the source file, either use AlphLite to correct any mistakes you made or, using OzTeX, pull down View, View nameoffile.dvi to preview it. If you like what you see, you can pull down File, Print nameoffile.dvi to send it to the printer.