Firewall rules are more fine grained filtering rules for filtering your traffic.
At the top of the page is a list of selectable interfaces.
When a particular interface is selected, details about it is shown in the configuration section.
Where applicable, the configuration is divided into separate sections for source and destination zones.
If you have networks/devices set up, you can add them to the zone.
To add a device as a zone member:
The Select network device dialog opens.