C#:

// Create new navigation item
PaneItem item = new PaneItem();
item.Header = "Item Text";
// Assing the image to item.Image and item.ImageSmall
// Assign content to the item
DockPanel panel = new DockPanel();
panel.Background = Brushes.Yellow;
// Add some content to panel.Children collection
panel.Children.Add(new CheckBox());
// Assign panel to the navigation item
item.Content = panel;
// Add item to NavigationPane controls
navigationPane1.Items.Add(item);

VB:

' Create new navigation item
Dim item As New PaneItem()
item.Header = "Item Text"
' Assing the image to item.Image and item.ImageSmall
' Assign content to the item
Dim panel As New DockPanel()
panel.Background = Brushes.Yellow
' Add some content to panel.Children collection
panel.Children.Add(New CheckBox())
' Assign panel to the navigation item
item.Content = panel
' Add item to NavigationPane controls
navigationPane1.Items.Add(item)