Change WAN DNS Server

I have two WANs (eth0 and eth1), when I originally them up the DNS is pointed to 8.8.8.8 and I want to change to 208.67.222.222. I've looked all over the GUI and can't find where I can simply change the DNS for each WAN. Is there a simple way to change the DNS for each WAN? I know it will be an easy answer but I can't find it.

Thanks in advance for your help.