Add Additional NIC Cards

How do I add additional Netwok cards to Mepis. By default under OS Options I can configure 2 NIC cards eth0 and eth1. I need to add and configure a third NIC card, is this possible and if so what files do I need to edit to configure the card. I'm new to Linux but I know how to open and edit files with Kedit.
I appreciate any help you can give.

Thanks in advance.

Rog