First, create all pages you need to build a structure with.
![Image Placeholder](/desk/file/3498246/image.png)
than, go to the page you want to make subpage and apply a parent page to it. You can do it in the page settings.
![Image Placeholder](/desk/file/3498247/image.png)
than, the page is seen in the tree view as a subpage.
![Image Placeholder](/desk/file/3498245/image.png)
in order to display it on the native main menu, you need first,to override the main menu module to make it recognize our structure.
![Image Placeholder](/desk/file/3498248/image.png)
actually, that's all. Than you can go to the main menu and see the AdCMS block in the left part of available blocks.
![Image Placeholder](/desk/file/3498249/image.png)
so you can handle it like any other block in this menu and apply a parent page to your active pages. The submenu will be created than.