how to open rad window

<link href="StyleSheet.css" rel="stylesheet" type="text/css" />
   
            

</head>
<body>
        <form id="form1" runat="server">   
        <telerik:RadScriptManager ID="RadScriptManager1" runat="server" />

        <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server">
       
        </telerik:RadAjaxManager>
            &nbsp;&nbsp;
            <telerik:RadSlider ID="RadSlider1" IsSelectionRangeEnabled= ...