Assuming the model of DSL router has an inbuilt 4-port switch or an ethernet interface you should be able to attach to your local network that your solaris host is connected to....assigning a suitable IP address to the ethernet interface of the router if needed.
If you have a standalone Solaris host then just set-up a network interface for DHCP and connect to the router directly (cross over UTP cable probably req'd for a single ethernet model).
DNS (nameserver) config will be supplied by your ISP....assign the IP address of the routers ethernet interface as your default gateway....and away you go...

One additional point to add is assuming you are connecting the DSL router to the internet....remember to invest in some good firewall software and disable all unnecessary tcp/udp ports on the interface facing the router.