DNS is potentially a very complicated subject, but StarV3 is just setup as a recursive DNS resolver.
DNS Configuration in StarV3
system --> services --> dns server --> configure service
Choose "load service on boot" here.
system --> services --> dns server --> service activation
Start the DNS server here.
That's all there is to it, turn it on or turn it off. Point your clients at it and it'll perform recursive DNS lookups for them.