Add content to GUILayout.Window

How do I add content to my GUILayout.Window, here is my code, I want to add a few sentences into the window before the button:

 var windowRect : Rect = Rect (20, 20, 120, 50);
 private var carName : String;
 private var carDesc: GUIContent;

 function OnGUI ()
 {
    windowRect = GUILayout.Window ( 0, windowRect, DoMyWindow,
                                    carName, GUILayout.Width (300));
 }
   
 function DoMyWindow (windowID : int) { // This button will size to fit the window
   if (GUILayout.Button ("Select Car"))
     print (carName + " is selected, move to track selection scene.");
 }