Design and Config Help

[jenmonk]

Hello OPNSensers

I have gateway router (gigapower att) and RT-n68u in current setup. wifi disabled in gateway router and connected to rt-n68u in bridge mode. rt-n68u dhcp on.
I want to have my setup as
gateway router bridge mode to OPNSense (WAN ?)
OPNSense -- RT-n68U. (LAN ?)
Enable DHCP in OPNSense.
Appreciate All your help
Thanks
Bala