If you want to add new (horizontal or other) menus to DokuWiki you have to select another template with such menus, edit the default one or create your own. See http://www.dokuwiki.org/Template
To get the same buttons as www.dokuwiki.org at the top of the page (using default template) just add a file called
topheader.html in lib/tpl/default with HTML of your choice. This snippet will be added to every page in your wiki.