The easiest way to add google fonts is by using WP Google Fonts plugin: https://wordpress.org/plugins/wp-google-fonts/ 

In a child theme functions.php add the following code


add_action('wp_enqueue_scripts', 'wpestate_scripts_childtheme');
function wpestate_scripts_childtheme() {
$protocol = is_ssl() ? 'https' : 'http';
wp_enqueue_style( 'wpestate-railway', "$protocol://fonts.googleapis.com/css?family=Raleway:500,600,400,700,800&subset=latin,latin-ext" );
}


Now, you need to replace the raleway font in the above example with your font. Open the google fonts page and click quick use for your font. You should have something like in the image below

Select the font styles from the list like bold, semi-bold etc. In “Add this code to your site ” section copy the string after  ?family= and replace it in the function above.