How Can I use ICS behind a NAT?

my pc is connected through a residential gateway (router) which IP address is already set to 192.168.0.1. now i'm trying to experiment on sharing that connection by trying a hotspot using my wlan adapter only. but the software i'll be using suggests that i need to be the gateway, or map a port number. How could i successfully do that, using my pc already connect to a LAN?