Which ports does Warzone use?
Note that you only need to open ports for hosting games. You can join and play any games you want without configuring port forwarding.
Multiplayer doesn't work!
If your router supports UPnP, Warzone can set up the required ports by itself. See if you can enable UPnP in your router settings.
Otherwise, if you want/need to set it up manually, make your router forward TCP port 2100 to the machine that is doing the hosting, and make sure no firewalls block that port.