Simply enter the following line into the Terminal window. Note that you may need to use "Wi-Fi" instead of "Ethernet" if that is the connection you're using. Also, my router's IP is 192.168.1.1. You may need to change this number for your Router address.
sudo networksetup -setadditionalroutes Ethernet 184.169.174.0 255.255.255.0 192.168.1.1 184.169.137.0 255.255.255.0 192.168.1.1 184.169.154.0 255.255.255.0 192.168.1.1
I hope this helps others. It took me a while to find...