Cómo agregar un checkbox de privacidad a mi formulario de contacto

// Contact Form
function theme_shortcode_contact_form($atts, $content = null) {
	global $arContactFormSubmitStatus;
	
	extract(shortcode_atts(array(
		'form_name'		=> 'default',
		'submit_label'	=> 'send email'
    ), $atts));
	
	$strSuccessMessage = (get_option_tree('thank_you_message') != '') ? get_option_tree('thank_you_message') : "Your message was sent - we will get back to you as soon as possible!";
	
	$output  = '<div id="contact_form_'.$form_name.'" class="contact_form sticky_note width_940">';
		$output	.= '<div class="inner">';
			$output .= '<form action="'.get_permalink().'" id="contact_form_'.$form_name.'" method="post">';
				$output .= '<fieldset>';
					$output .= '<ol>';
						$output .= '<li';
						
						if(isset($arContactFormSubmitStatus[$form_name]['errors'][$form_name.'_contact_name'])) {
							$output .= ' class="error"';
						}
						
						$output .= '>';
							$output .= '<label for="'.$form_name.'_contact_name"><span>Nombre:</span></label>';
							$output .= '<div><input type="text" name="'.$form_name.'_contact_name" id="'.$form_name.'_contact_name" value="';
							
							if(isset($_POST[$form_name.'_contact_name'])) {
								$output .= $_POST[$form_name.'_contact_name'];
							}
							
							$output .= '" class="requiredField" placeholder="Escriba su Nombre..." /></div>';
						$output .= '</li>';
						
						$output .= '<li';
						
						if(isset($arContactFormSubmitStatus[$form_name]['errors'][$form_name.'_contact_email'])) {
							$output .= ' class="error"';
						}
						
						$output .= '>';
							$output .= '<label for="'.$form_name.'_contact_email"><span>Email:</span></label>';
							$output .= '<div><input type="text" name="'.$form_name.'_contact_email" id="'.$form_name.'_contact_email" value="';
							
							if(isset($_POST[$form_name.'_contact_email'])) {
								$output .= $_POST[$form_name.'_contact_email'];
							}
							
							$output .= '" class="requiredField" placeholder="Escriba su email..." /></div>';
						$output .= '</li>';

						$output .= '<li class="textarea';
						if(isset($arContactFormSubmitStatus[$form_name]['errors'][$form_name.'_contact_name'])) {
							$output .= ' error';
						}
						$output .= '">';
						
							$output .= '<label for="'.$form_name.'_contact_message"><span>Mensaje:</span></label>';
							$output .= '<div><textarea name="'.$form_name.'_contact_message" id="'.$form_name.'_contact_message" rows="6" cols="50" class="requiredField elastic" placeholder="Escriba su Mensaje...">';
							

							
	
							
							if(isset($_POST[$form_name.'_contact_message'])) {
								$output .= $_POST[$form_name.'_contact_message'];
							}
							
							$output .= '</textarea></div>';
	
						$output .= '</li>';
						
					$output .= '</ol>';
					$output .= '<button type="submit" class="submit">Enviar Formulario'./*.$submit_label.*/'</button>';
					$output .= '<input type="hidden" value="'.$form_name.'" class="form_name" name="leap_contact_form" />';
					$output .= '<div class="error_status"></div>';
				$output .= '</fieldset>';
				$output .= '<div class="successMessage" style="display:none">' . $strSuccessMessage . '</div>';
				
			$output .= '</form>';
			$output .= '<div class="contact_info">';
				$output .= do_shortcode($content);
			$output .= '</div>';
		$output .= '</div>';
		$output .= '<div class="tape"></div>';
	$output .= '</div>';
	
	return $output;
}

add_shortcode('contact_form', 'theme_shortcode_contact_form');


function theme_shortcode_toggle($atts, $content = null) {
	extract(shortcode_atts(array(
		'topic'			=> 'Click me to expand!'
    ), $atts));

	if(!$content) {
		$content = 'Whoo, I\'m expanded. I was getting uncomfortable being collapsed like that.';
	}

	$output  = '<div class="toggle">';
		$output .= '<a class="topic" href="#">' . $topic . '</a>';
		$output .= '<div class="description">';
		$output .= $content;
		$output .= '</div>';
	$output .= '</div>';

	return $output;
}

add_shortcode('toggle', 'theme_shortcode_toggle');