If your Linksys is set-up to assign dynamic IPs to your networked computers, then you can select DHCP... Dynamic Host Control Protocol, maybe? When the system boots, it will send a request to the network for an IP, and the Linksys will give it one.
If your Linksys isn't set-up to assign dynamic IPs, then you will have to select static. Fill in the IP of the computer, the IP of the Linksys as the gateway, and the IPs of a couple DNS computers. Your DSL company should have provided those.