Finally you will need to specify the location for this menu. As mentioned above, the Ella theme contains 1 possible menu location; the Main Menu.
To assign the Main Menu
Go to Appearance> Menus in the main admin menu.
At the top left of that page you will see a panel titled Theme Locations
Here there will be a select box under the two available locations in the Ella theme.These select boxes will hold a list of all created menus.
so select the menu you wish to place in the Main Menu location from the drop down and then click Save.