Go to Control Panel > Network and Sharing (or Network and Internet in Windows 7), and then click the Change adapter settings link.
Right-click the connection (typically says Wifi) and then choose Status from the context menu.
In the Ethernet Status window, click Details.
The Network Connection Details window will have the information you want. Note that the MAC address is listed as the Physical Address.
Please write down the Wi-Fi MAC address for future reference.