DDRMenu is the default navigation provider in DotNetNuke 6, and is also available as an installable extension for versions of DotNetNuke from 4.5.0 onwards.

DNN 6 DDRMenu can be used in three different ways:

1.By dropping in ready-made templates, you can add a mega-menu, treeview, accordion, Superfish menu, sitemap, breadcrumb or many other types of navigation to a skin.
2.If you have an old skin that uses version 1 of DNNMenu, or even the old SolPart menu, you can very easily replace it with DDRMenu to provide exactly the same look but with true hyperlinks, improved SEO and better browser support.
3.You can take the starter templates provided, amend them as required, and incorporate them into your skins to produce just about any custom menu style you want.

DDR Menu in DNN 6 is already installed. For earlier versions of DNN 4 and 5,

1) Download the relevant installation package from http://dnnddrmenu.codeplex.com/.
2) Install the module in the host Module Definitions page.
3) The following entry should be added to web.config:
<add name="DDRMenuNavigationProvider" type="DotNetNuke.Web.DDRMenu.DDRMenuNavigationProvider, DotNetNuke.Web.DDRMenu" />

With the core menu installed, you will have the DNNMenu and SolPart upgrade templates available.

Download a template and drop the template into your skin folder or place it in your desktopmodules/ddrmenu if you want the menu style available to the whole DNN instance.

Add these two lines:
<%@ Register TagPrefix="ddr" TagName="MENU" src="~/DesktopModules/DDRMenu/Menu.ascx" %>
<%@ Register TagPrefix="ddr" Namespace="DotNetNuke.Web.DDRMenu.TemplateEngine" Assembly="DotNetNuke.Web.DDRMenu" %>

For upgrading a DNN Menu version 1 instance,Edit your skin's ASCX files and replace

<dnn:NAV providername="DNNMenuNavigationProvider" ...> with
<dnn:NAV providername="DDRMenuNavigationProvider" ...>

There are lot of customizations that can be done with DNN 6 DDR Menu. For instance, If you don't want to show all the pages in your menu,you can use the NodeSelector Option. Set NodeSelector to RootOnly  to show only root level menu items. NodeSelector to RootChildren to show all the children of the rootmenutiem that is the parent of the current page.

You can also use the IncludeNodes and ExcludeNodes options. These are generally used in DNN 4 and 5 to create separate menus for Admin and Host

In DNN 6, you can specify IncludeHidden="true" to include hidden pages in the menu structure. This can be useful for creating separate menus to show site sections that are hidden from the main menu.