It is unclear what Home and New Page really is. Hence I assume they are two categories that exists in your Magento instance.
In default RWD Theme which is available in Magento 1.9, only active categories will be added to topmenu section. This means that you can see only categories (which are active) by default in topmenu section. CMS Pages and static blocks will not be available as a topmenu item unless you have added them to topmenu section manually.
From your vague question, I think you have basically two questions.
How can I add a category as a sub-item of another category ?
This is how Men menu and it's children look like in default RWD theme
See the category settings in admin corresponding Men Category
As you can see, Men Category comes under Default Category. All sibling menu items of Men Category similarly comes directly under Default Category. You can also see, all sub-menu items of Men menu item is actually sub-categories of Men Category.
This is what you need to do in this case. If you need to make a sub-menu item for Home, then you need to put New Page as a sub-category of Home category.
How can I add a new topmenu Item ?
Magento provides two events to add your custom topmenu items in topmenu tree. They are :
If you do a close inspection,
Mage_Catalog module is observing to the event
page_block_html_topmenu_gethtml_before and adding categories as topmenu items via observer. You can use this classic example to create your own custom menu tree and then add it to the topmenu tree. All you need to do is observe to this either of these events and add your menu item.
You can add a CMS Page as a topmenu item or any other custom page as topmenu item using these events.