The tree view pane displays the configured Front End Processors (FEPs) and the Intelligent Electronic Devices (IEDs) that are associated with them.

The Unassociated node at the top of the tree view contains any IEDs not currently associated with a FEP. The Unassociated node is where new IED instances are created and updated until ready to be made active. If you right-click a tree node, the context menu will display various operations that can be performed on the selected item.