functions.php

add_action( 'wp_enqueue_scripts', 'child_load_google_font' );
/**
 * Enqueue Google Font
 * 
 * @author Greg Rickaby
 * @since 1.0
 */
function child_load_google_font() {

  	$protocol = is_ssl() ? 'https' : 'http';
		$query_args = array(
			'family' => 'Open+Sans' // Change this to whatever font you'd like
		);
 
	wp_enqueue_style( 'child-fonts', add_query_arg( $query_args, "$protocol://fonts.googleapis.com/css" ), array(), null );
}