The Easy Way to Add Custom CSS in WordPress
Since WordPress 4.7, it has become easier to add custom CSS to your WordPress site.
The best part is: this doesn't require extra plugins at all. This feature is already part of the core.
You can insert your CSS in a three step process. In this post we'll show you how.
- Login into your WordPress site.
- Click “Customize” in the admin toolbar.

- Click the “Additional CSS” tab:

- Add your custom CSS into the “Additional CSS” box.
- Click the “Save & Publish” button.

That's it! Go to the front of your site and your custom CSS should be in action.