To have specific menu items appear as sub items, you must assign them to the specific navigation item in which they will originate from. The following tutorial will show you how simple it is to create your ideal menu system.
You will then be transported to the Menu Manager for primary links. At this point, you can do two things. The first is to edit an existing menu item, which we will be doing in this tutorial or create a New menu item to be subordinate to an existing item. Click on the item you want to be part of the dropdown menu.
You can now assign the content item to the mainmenu item in which you want to be in the dropdown menu. Identify the "Parent Item" section of the manager. You will select the item in which you wish to be the parent and the source of the dropdown menu.