192.168.xxx.xxx are reserved for private networks, so those will be fine for you.

For PC's not connected directly to the internet, set the default gateway and preferred DNS server to be the IP address of the PC which is connected to the internet.

For the PC connected to the internet, leave the default gateway empty and preferred DNS set to obtain automtically.

Think that should do it, but there is plenty of help on the net if you get any particular problems.

Phill