From the main menu, click on Menus

Expand the Menus tree and click on the Menu Category that you wish to add your menu item to, then click on + Allocate Menu Item

Select the menu item(s) that you want to add to your menu category – as you click on one menu item, it will disappear from the list.

When you are done, click on the X mark at the top right of your screen to close that window.

The menu item has now been added to your menu category.

You can easily remove a menu item from a menu category by clicking on the Delete icon for that menu item.