You have to set a custom control template for the chart.

If your chart is defined in c#, the easiest way to do this would be to create a control template in xaml and add it to the page resources, then assign it to the chart in code. Otherwise, you'll have to create the entire template in c#

<UserControl.Resources>
   <ControlTemplate TargetType="igChart:XamWebChart" x:Key="ChartTemplate">
      <Border BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
         <Grid x:Name="RootElement" Background="{TemplateBinding Background}" Margin="{TemplateBinding Padding}" >

         <Grid.RowDefinitions>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="Auto"/>
            <RowDefinition Height="*"/>
         </Grid.RowDefinitions>

         <Grid x:Name="CaptionPanel" Grid.Row="0"/>
         <Grid x:Name="LegendPanel" Grid.Row="1"/>
         <Grid x:Name="ScenePanel" Grid.Row="2"/>
         </Grid>
      </Border>
   </ControlTemplate>
</UserControl.Resources>

private void UserControl_Loaded(object sender, RoutedEventArgs e)
{
   XamWebChart chart = new XamWebChart();
   chart.Series.Add(new Series());
   chart.Series[0].DataSource = new int[] { 1, 2, 3 };
   ControlTemplate chartTemplate = this.Resources["ChartTemplate"] as ControlTemplate;
   if (chartTemplate != null)
   {
      chart.Template = chartTemplate;
   }
   LayoutRoot.Children.Add(chart);
}