Method 1: Installing a third party WordPress Plugin
Method 2: By editing function.php file of the active WordPress Theme
In this method, you would need to ftp to your installed and currently active WordPress theme directory and look for the file called functions.php. You will then need to hook a new PHP function that gets loaded right after the WordPress Post’s <head> section gets loaded. Below is an example of how to write such a hook function in your functions.php file.
In addition to this, you can add custom CSS to your post using “Additional CSS” option under Theme Customization option you get when you go to the “Appearance” option in the WordPress Admin dashboard.
Until next time, happy coding 🙂 !!