Port Forwarding and Static IP with a Netgear Nighthawk MR1100

I am using a Netgear MR1100 for AT&T.  Port forwarding is not working.  I have logged into the router and disabled DHCP, and I can see the MAC address of the connected console, but I cannot figure out where to obtain the static IP address which I would then enter into the Port Forwarding section.  Please help.