GUI Builder makes creating a split pane simple. From the menu bar on the main GUI Builder window, select File --> New File.
From the menu bar on the GUI Builder File window, click
the Insert Split Pane tool button 
to display a panel builder where you can insert the
components you want in your split pane. In the following example, two components
are added.
Figure 1: Creating a Split Pane with GUI Builder 
After you create the split pane, click the Preview tool
button 
icon to preview it, as shown in Figure 2.
Figure 2: Previewing the Split Pane with GUI Builder 