how to host a ftp website from home?

I have a cable modem at home, i would like to host a ftp website from home. my question is i have a Toshiba 5000 cable modem/firewall/router at home, all my computers is getting IP from the toshiba box, which is 192.168.100.* address. When I ping from out site I only can ping the router, not the computer behind that. how should i setup the system to host the ftp server?