Search “change adapter settings” in the desktop search or press the key combination “Win + R” and enter “ncpa.cpl”

If neither of these work, you can get there via the control panel.

When you are in adapter settings, find the network adapter you need to know the MAC address of, right click it and select Status, then go into the details option and find the physical address there.

In windows 10 you can also open the networks list, select the “Network Settings” option then go into “Advanced options”