2 nic cards

How do I config one NIC for WAN and the other for LAN, if the WAN is a different subnet on a SBS 2003 with Exchange. The WAN NIC (NIC 1)is connected to ATT UVerse and the LAN NIC (NIC 2)is connected to a local network switch. I can get to the internet on all client computers but cannot get to the shared files on the server.