Hi,
I assume you are asking about adding menus in asp.net web app at design time. It is simply adding th markup in the master file (if the menu has to appear in all the pages)
The example can be seen when you open the default master aspx file (site.master). Add the menu items hierarchially.
<asp:menu id="NavigationMenu" runat="server" cssclass="menu" enableviewstate="false" includestyleblock="false" orientation="Horizontal" xmlns:asp="#unknown">
<items>
<asp:menuitem navigateurl="~/Default.aspx" text="Home" />
<asp:menuitem navigateurl="~/About.aspx" text="About" />
<asp:menuitem text="Hospital Management" value="Hospital Management">
<asp:menuitem navigateurl="~/department.aspx" text="Department">
Value="Department"></asp:menuitem>
<asp:menuitem navigateurl="~/nursing.aspx" text="Nursing Department">
Value="Nursing Department"></asp:menuitem>
</asp:menuitem>
</items>
</asp:menu>
If you are asking about adding menus at runtime, then please explain more what exactly you want