EX3301 T0 Port Forwarding issue

Hi, I'm a newb to the EX3301 T0 Router, in the past, I've simply used an external domain and pointed it at the router and forwarded the necessary ports. Following the same logic the ports appear not to be forwarded although the domain is pointing at the router. I suspect there are additional rules that need setting up, and advise or pointers or tutorials would be appreciated….. thanks