Two NIC cards for ISA 2004

Hey all, and thanks for your time. Do I need two NIC cards to configure ISA? I have a domain (with SSL cert) that points to a Windows SBS 2003 server. This is the only server on the lan and is intended for webhosting and Exchange hosting. I installed ISA 2004 and I can connect to my Exchange OWA and even RPC over HTTP through Outlook. I just am not sure how to use the second NIC card or even how it is intended to be configured. Any advice or articles related would be greatly appreciated. Thanks =]