Captcha

How do I use Captcha control on my page

 <div style="text-align: center;">
   <asp:textbox id="tbxCaptcha" runat="server" width="254" font-size="12px" tooltip="Enter the word displayed in the image above." autocomplete="off" /><br /><br />
    <asp:image id="imgCaptcha" runat="server" imageurl="/Captcha.ashx?UniqueId" alternatetext="CAPTCHA" /> <a style="font-size: 0.8em;" href="Captcha.aspx">Reload</a><br /><br />
    <asp:button id="btnVerify" runat="server" width="254" text="Verify" validationgroup="Verify" onclick="btnVerify_Click" /><br />
     <div id="divAlert" runat="server" class="alert" style="text-align:center;"></div>
   </div>

 if (Centralpoint.Web.UI.HttpHandlers.Captcha.IsValidCode(tbxCaptcha.Text, "UniqueId"))
     divAlert.InnerText = "SUCCESS";

else
     divAlert.InnerText = "FAILURE";