Magento - 将根类别链接添加到菜单

I am new to Magento and I don't know how to link the root category to the menu. It seems that there is no option for this in the backend.

Any idea on how to implement this?

Thanks!

Create a new Category under the root category and put all category there in.

$rootcategory_id = Mage::app()->getStore()->getRootCategoryId();
$collection = Mage::getSingleton('catalog/category')->load($rootcategory_id);
$rootcaturl= $collection->getUrl();//default category url i.e root category of the store