Complete Custom Style Part of Site

1. FTP/Server access: Navigate to your WP install and look in /wp-content/themes/[your theme folder]
2. Via the WP Dashboard: Appearance > Editor, then look for Theme Functions (functions.php) in the right column

Add the following to add a custom style sheet (replace “custom-style.css” with a better style sheet name, and replace ‘your-page-slug’ with the slug of the page you wish to add the custom style to):

// script manager template for registering and enqueuing files
function childtheme_script_manager() {
    // register custom style on your specific page
    if (is_page('your-page-slug')) {
        wp_register_style('custom-css', get_stylesheet_directory_uri() . '/custom-style.css');
        wp_enqueue_style ('custom-css');
    }
}
add_action('wp_enqueue_scripts', 'childtheme_script_manager');

Create a style sheet in your theme folder called custom-style.css. Add your custom styles. Write the css to target whatever it is on your page that needs specific styling. Without anymore information or posting example code on that page, it’s impossible to answer that.