Westell support will probably refer any calls on this product model to Verizon as their website support section does. See page 107 of your router's
User Guide. The general gist of forwarding is selecting an external port number(s) for the WAN interface, say tcp 8080, and then entering the internal address, say 192.168.1.10, and port number, say tcp 80, that any traffic received on that port on the WAN interface should get routed to. So for my example numbers, any web browsers attempting to connect to your router's external address on port 8080 tcp would passthrough your firewall and connect to 192.168.1.10:80. Be very careful to only forward the minimum ports necessary as forwarding all ports will quickly result in your LAN being compromised by outside parties.