When you are constructing your HUGIN network, you are running in Edit Mode. In Figure 1 you can see a network window of a HUGIN network running in Edit Mode. In Edit Mode, the network window is split up in a Tables Pane containing the table of the currently selected node. Below the Tables Pane is the Network Pane where the graph describing the network is found.
To switch from Run Mode to Edit Mode, press the Edit Mode tool button (see Figure 2).