Reply To: Custom Font

Try to add the following PHP code snippet to the child theme functions.php file

function select2_enqueue() {
    wp_enqueue_script(
        'select2-js',
        '//cdn.jsdelivr.net/select2/3.5.2/select2.min.js',
        array(),
        '3.5.2',
        true
    );
    wp_enqueue_style(
        'select2-css',
        '//cdn.jsdelivr.net/select2/3.5.2/select2.css',
        array(),
        '3.5.2',
        'all'
    );
}
add_action( 'admin_init', 'select2_enqueue' );