Not many people use Macs for server purposes. They're probably capable, but typically Macs aren't thought of as server machines.
I know absolutely nothing about Macs, but I can tell you what to do if you were on a Windows or Linux box. There is a file called httpd.conf in a conf subdirectory of the main apache dir. You need to open this file in any text editor and configure the various options in there.
Also, when you start it you're not going to see anything special happen. It's a server app, so it just runs in the background waiting for you to request something from it. With it running, go to http://localhost/ and you should see the default page it's serving.