When you’re developing your own theme, “enqueuing” is the most correct way call your stylesheets. But simply doing that won’t add add versioning.

Here’s an example that you can put in your functions.php file…

add_action( 'wp_enqueue_scripts', 'my_theme_enqueue_styles' );

function my_theme_enqueue_styles() {
	wp_enqueue_style('main-styles', get_template_directory_uri() . '/style.css', array(), filemtime(get_template_directory() . '/style.css'), false);	
}

The above code adds your stylesheet to every page, along with a timestamp that changes every time your save CSS file. This is great, because the browser will still cache your CSS (which improves load times) but will reset the cache whenever you update the CSS file.

The output will look something like this…

<link rel='stylesheet' id='main-styles-css'  href='/wp-content/themes/custom-theme/style.css?ver=1557348399' type='text/css' />

Source: www.launch2success.com/guide/force-css-changes-to-go-live-immediately-in-wordpress/www.launch2success.com/guide/force-css-changes-to-go-live-immediately-in-wordpress/