If I understand your requirement, it seems that you are trying to set the AXIS TITLE
property for the x-axis and the y-axis.
See the The Wizard Axis Tab
documentation for design time settings.
If you're trying to define the titles server-side, then take a look at the Creating RadChart Programmatically - more complex example
// Set text and line for X axis
radChart.PlotArea.XAxis.Appearance.Width = 3;
radChart.PlotArea.XAxis.Appearance.Color = System.Drawing.Color.Red;
// Set text and line for Y axis
radChart.PlotArea.YAxis.Appearance.Width = 3;
radChart.PlotArea.YAxis.Appearance.Color = System.Drawing.Color.Red;
Hope this helps!