I just figured it out !
Here is an basic example about creating a line graph with ZedGraph
private void button3_Click(object sender, EventArgs e)
{
double[] y = { 1, 2, 3, 9 ,1,15,3,7,2};
string[] schools = { "A", "B", "C", "D" ,"E","F","G","H","J"};
var pane = zg1.GraphPane;
pane.XAxis.Scale.IsVisible = true;
pane.YAxis.Scale.IsVisible = true;
pane.XAxis.MajorGrid.IsVisible = true;
pane.YAxis.MajorGrid.IsVisible = true;
pane.XAxis.Scale.TextLabels = schools;
pane.XAxis.Type = AxisType.Text;
LineItem pointsCurve = pane.AddCurve("", null, y, Color.Black);
pointsCurve.Line.IsVisible = true;
pointsCurve.Line.Width = 3.0F;
pointsCurve.Symbol.Fill = new Fill(new Color[] { Color.Blue, Color.Green, Color.Red });
pointsCurve.Symbol.Fill.Type = FillType.Solid;
pointsCurve.Symbol.Type = SymbolType.Circle;
pointsCurve.Symbol.Border.IsVisible = true;
pane.AxisChange();
zg1.Refresh();
this.Controls.Add(zg1);
}