When you create a new URL forward you simply enter the IP address in the destination URL field. Please note you must be able to type the IP address into a web browser and have your web page load in order to use your IP with URL forwarding.

As per usual, the nameservers must be ns1.webcity.com.au and ns2.webcity.com.au.

If you are hosting multiple websites on your fixed IP, you will need to use dns hosting in order to set your A records to point to your IP.