How to connect to the four Ethernet ports on a wireless router?

Let's say we are happy with our typical wireless router. But one day we notice it has four LAN ports. We connect an Ethernet cable from one of them to our computer. On our computer do we use: * dhclient and the same SSID and password as we used for wireless? * pppoe and the same userid and password our ISP gave us? * One of the above, with no username or password?