Port Forwarding and IPChains

I have a Linux-Mandrake 7.1 server that I want to use as a firewall. Part of this firewall is to forward port 80 and 21 to an NT web server on my private LAN. I cannot find any good answer on how to do this. Can someone provide the syntax for loading the correct program and the proper IPChains commands to make this happen ? Here are sample ip addresses to use: Linux server public ip address = 62.130.119.3. Linux server private LAN IP = 192.168.1.1. My NT server is 192.168.1.2. All subnet masks are 255.255.255.0.

Thanks for your help !
David