You most certainly do have a subnet for your private network. The subnet for 192.168.0.X is a standard class C subnet (*), /24 or 255.255.255.0. Beyond that, all you would need to do is specify the gateway for the network, and the DNS servers. You can do fancy things, like put a MAC address into the configs so that machine always gets the same IP address from the server, or give certain machines (again based on MAC) get a different address scheme than others. Most all of those things are not necessary for a simple network, but all things are possible.
(*) You could if you so elect not make a 192.168 network have a 255.255.255.0 subnet. You could make it larger or smaller, but well north of 99% of 192.168.X.Y subnets will have 255.255.255.0 subnets.
I don't have a config for you, but a sample from google should suit you fine.