The following line of code will help you to set the IP address and the subnet mask:
netsh int ip set address name = "LAN" source = static addr = 127.0.0.1 mask = 255.255.255.205
Of course, you have to use real IP address instead of samples given above (127.0.0.1 and 255.255.255.205).
Also we advice you to learn netsh command because it's really useful for different networking operations.