Unlike iOS, macOS doesn’t give you an option to randomize your MAC address in the settings, so you’ll need to do it with a command or a script.
# You open up your Terminal and enter this command to randomize your MAC address:
openssl rand -hex 6 | sed 's/\(..\)/\1:/g; s/.$//' | xargs sudo ifconfig en1 ether
# en1 is the name of the interface you're changing the MAC address for.
# This might not be the right one on every Mac,
# so to check you can hold the option key and click the Wi-Fi symbol at the top right of your screen.
# This will be reset on reboot.