Setting up DMZ on Fios Router

I'm trying to set up my own router (Dlink) to go with my Fios router (G1100).  My reading/research tells me that the best way to do this is to set up a DMZ to my Dlink router.  My Fios router is connect to the WAN port on the Dlink.  My problem:  the Fios DMZ setup only allows me to change the last octet of the IP address, yet I need to change it to match the IP address of my Dlink router (192.168.0.1) which means I'll at least need to be able to change the 3rd octet (everything is greyed out except the 4th octet).  What am I missing?  Thanks in advance.