A menu bar is a set of hierarchical pieces which contains menu items.
What is the Use Of Menu?
Menus let your site visitors navigate directly to URLs on your site. Organizing and placing menus well can help direct your users to the parts of your site you consider most important.
How To Configure a Menu?
If you want to add a menu on the Content Panel Header or in Layout container, you need to go to the customize page and add the Menu(item types) as child to either a layout container or content panel.
Step 1:

Step 2:
To create a menu item under the menu.
Now create a new item and select the Child to Menu as Menu item.
The menu items can be of 1)Check box menu item 2)Menu item 3)Radiogroup menu 4) Separator menu item.
Menu Item:
Create a child to menu item by clicking on the new button.
Select the item type as TriggerOnClick.
Now create a child to trigger on click and add a button action which ever you feel like, will suit your requirement.
Example: This is how the Menu Item looks like.
Checkbox Menu Item:
This provides a checkbox towards the left of the menu item.
Radiogroup Menu Item:
This provides a radio button to the left of the menu item.
Seperator Menu Item:
This provides a demarcation line .