I found that there are at least two methods to assign a spoofed MAC address to my network connection:
Assign a MAC address to a connection using "Edit connection" GUI in WiFi (or Ethernet) tab inside "Cloned MAC address" edit box.
Assign a MAC address to wlan0 using ifconfig command:
sudo ifconfig wlan0 down sudo ifconfig wlan0 hw ether xx:xx:xx:xx:xx:xx sudo ifconfig wlan0 up
Now, my question is, what is the difference between these two ways?