Would like to confirm if I understand home network routing correctly.

I want to open terminal on each computer, and type the following,
assuming each computer has assigned static IP address:
># sudo ifconfig eht0 192.168.1.66 netmask 255.255.255.0 up
># sudo route add-net 192.168.1.0 netmask 255.255.255.0 eth0
># sudo route add default gw 192.168.1.1 eth0

I hate to run the commands, if I cause permanent change and can't undo
it.  Is this the steps I take?
Thanks, Tom