There are two ways:

From the Handheld, go to the Web menu and hit enter. You'll see the IP address. Arrow down about 8 times and you'll see the Mac address.

From CBAS, if you have the controllers online (which you probably don't), In Real Mode, go to Hardware view and find the controller. Click on it then click Show Controller Diagnostics. At the bottom of the page you will find the mac address next to the serial number.