The Jenkins Wiki page tells you how to change settings like which port number Jenkins will listen to. These settings need to be specified on the command line when Jenkins is started.
For the Mac, Jenkins is deployed as a launch daemon. (If you want to know more about launchd and daemons, see here and here)
The launch daemon picks up the command line options from a standard preferences file, /Library/Preferences/org.jenkins-ci.plist. If the file does not exist, built-in defaults are used. The preference files are manipulated using the standard utility defaults.
To view all settings in the file, run: defaults read /Library/Preferences/org.jenkins-ci
To get the value of a single setting, run: defaults read /Library/Preferences/org.jenkins-ci SETTING
To set the value of a setting, run: defaults write /Library/Preferences/org.jenkins-ci SETTING VALUE
For more information, see man defaults
The list of settings supported by the Jenkins launch daemon (see documentation):
Additionally, you can set also these: