If you want to add custom CSS code to style your website, you can do that in the Additional CSS panel.
Intermediate and advanced WordPress users often customize their site by adding CSS code directly to the style.css file of their theme.
An easier solution for beginners is to add your custom CSS code to the Additional CSS panel in the WordPress theme customizer. This will allow you to make changes to your site and see them live on the right side of your screen.
When you start writing some CSS code, WordPress will automatically suggest attributes to you based on the letters you type. It will also display error messages if you have not written a proper CSS statement.