The first step is to configure the machine as a server on the World Wide Web. There are an incredible array of possibilities here. If you want to get into this in detail, I strongly recommend the book "Providing Internet Services on the Mac". My personal choice for http service on the Mac is Quid Pro Quo.
The next step is to obtain and install the javAPRS software. It is available on the TAPR server at ftp://ftp.tapr.org/pub/tapr/SIG/aprssig/files/javastuff/javaprs.zip
Unzip this file...included are example pages, and the file javAPRSprog.html. This document gives all the details on how to install, configure, and add javAPRS to a web page.
You will want to locate some good APRSdos maps of your area to use. These must be saved in the uncompressed format in order to work with javAPRS.
To start, set up a static page with a log file from Mac/WinAPRS. All of this will keep you busy for a while, but it needs to be working correctly before you are ready to serve up live data.
Your server will need a radio/tnc attached to the modem port and a copy of APRServe...when you are ready contact me, and I'll build you a version that only serves local data. Eventually I'll have the APRServe <--> APRServe linking working, so that each APRServe site runs the full program and is interconnected, providing redundancy.
Steve Dimse K4HG