To add your own custom CSS classes to the navigation menu items you need to go to Appearance -> Menus.
In the top right corner of the screen you will see Screen Options.
![](https://kairaweb.com/wp-content/uploads/2019/07/menu-classes-01-1024x530.jpg)
Open the Screen Options drop down and select the CSS Classes box to turn this option on.
![](https://kairaweb.com/wp-content/uploads/2019/07/menu-classes-02-1024x730.jpg)
You will now see CSS Classes (optional) available under each menu item.
Add your custom CSS classes to the menu item you choose.