A menu bar is part of a window, while a popup menu can be shown on a window. Other than this difference, the two types of menus behave in a consistent way, as far as a user is concerned. Both of them are composed of click-able menu items.
First, let's look at how menu bar items and popup menu items can be retrieved so White can click on them.
//POP UP MENU
window.Get<ListBox>("listBoxWithPopup").RightClick();
PopupMenu popupMenu = window.Popup;
Menu level2Menu = popupMenu.Item("Root", "Level1", "Level2");
level2Menu = popupMenu.ItemBy(SearchCriteria.ByText("Root"), SearchCriteria.ByText("Level1"), SearchCriteria.ByText("Level2")); //can use any other search criteria as well.
//MENU BAR
MenuBar menuBar = window.MenuBar;
Menu level2Menu = menuBar.MenuItem("Root", "Level1", "Level2");
level2Menu = menuBar.MenuItemBy(SearchCriteria.ByText("Root"), SearchCriteria.ByText("Level1"), SearchCriteria.ByText("Level2")); //can use any other search criteria as well.
level2Menu.Click();
"Root" is one of the menus in the first level, "Level1" is inside "Root" menu and "Level2" is inside "Level1". So on.
"Root", etc are text of the menu visible to user.