Thank You for helping me.@korenisko not through the UI, but read this for some hints
So with this command I will open firewall for accessing this subnet from wan?
iptables -t nat -A POSTROUTING -s 192.168.2.0/24 -o eth3 -j MASQUERADE
after this command I see, I open web ui and add route, but what ip to Gateway? 192.168.1.1 ? No two routers, only one.