You can find the Netflow Settings at Services → Netflow.
Netflow is used for collecting network traffic data and emiting it as NetFlow flow towards a specified collector.
Before you can use the Netflow it has to be installed. You can install it at System → Addons.
You can create multiple netflow instances, each will send the data to a collector.
On the page the Netflow can be created, updated, enabled or disabled.
Interface to listen to traffic to.
Filter is a TCPDump style filter expression selects which packets will be captured. If no expression is given, all packets on the interface will be captured.
Version is the Netflow Version and 5 by default.
Remote IP Address defines the Remote Netflow collector IP Address.
Remote Port is the Remote Netflow collector Port and 2055 by default.