Sorting Template Columns in a Datagrid

[versacestl]

My data grid is set to allow sorting..

I have looked up a few ways to do this and am Still a bit unclear.
What steps need to be taken from here to make the column header a link to make the dataset coming in 'Asc' , 'Desc' Sortable..

I am using C# in the back

<asp:TemplateColumn SortExpression="Email_Add" HeaderText="Email Address">
<HeaderTemplate>Email Address</HeaderTemplate>
  <ItemTemplate>
            <asp:Label id=lblEmail_Provided Font-Bold="true" Runat="server" Text='<%# DataBinder.Eval(Container, "DataItem.Email_Add") %>'	
            </asp:Label>
    </ItemTemplate>
</asp:TemplateColumn>