I wonder that too recently and while playing around what I did to get it working was: to define a new menu using MenuDefinition
MenuDefinition NewMenu = new MenuDefinition("NewMenu", new LocalizableString("NewMenu", YourProjectNameConsts.LocalizationSourceName));
Populate that newly defined menu with fresh items:
NewMenu.AddItem(
new MenuItemDefinition(
"YourPage",
new LocalizableString("YourPage", GreenPlainsConsts.LocalizationSourceName),
url: "#/YourPage",
icon: "fa fa-home"
)
);
And eventually add newmenu the the menus mentioned in the documentation:
context.Manager.Menus.Add("NewMenu", NewMenu);
There you have it! This code might not be of the best quality so it should be reviewed by a master.