The first step is to click on the "Wireless Network" icon that should be at the top right on your statusbar;
Click on "Open Network Preferences ..." at the bottom;
Make sure you have selected your Wi-Fi connection in the list on the left and then click on the "Advanced" button at the bottom right;
The MAC Address is highlighted in the image above.
Wireless Networking Icon |
Network Preferences |
Advanced Network Settings |