A TRUE DMZ (not the thing that Linksys routers have) requires 2 firewalls.
internet---->firewall---->DMZ host---->firewall---->internal network
It cant draw it, but the DMZ host has 2 nics (one on each network) and there is no route from the internet to the internal network. All access is done via a proxy in the DMZ.
This is very secure once you setup all the rules on both firewalls, but not very practical.
Now, what I think you want is how to make a host DMZ in your router. Basically just find the place in the configurator webpage thing and put the IP of the host you want to be DMZ.