how to configure public ip

i have an external static ip supplied by isp
124.178.246.181 and a siemens speedstream 4200 router. What i want to do is setup live webserver using my public external ip 124.178.246.181, but dont know how to do it. I understand port forwarding, but dont understand NAT and cant find any tutorials to setup my externalpublic ip, because all tutorials only explain setting up compputer static ips.
Can anyone help please
Marea Australia