HOW DO I CONFIGURE TWO NETWORK CARDS

At the company where i am working there is already an existing LAN with a DC.I am supposed to configure it into a VPN.I ve read some notesespecially on this same site and i think i will manage. The only prolm is that i dont know how i will configure the second NIC (which i am yet to install).which one should connect to the LAN & which one to the WAN.Will the IP Addreses change?

Somebody help me keep my job!

thanks
kt. zambia