How can I add HTML formating to 'Swift Mail tutorial' based PHP email?

//send the welcome letter
function send_email($info){
		
	//format each email
	$body = format_email($info,'html');
	$body_plain_txt = format_email($info,'txt');

	//setup the mailer
	$transport = Swift_MailTransport::newInstance();
	$mailer = Swift_Mailer::newInstance($transport);
	$message = Swift_Message::newInstance();
	$message ->setSubject('Thanks for entering the competition');
	$message ->setFrom(array('info@examplemail.com' => 'FromEmailExample'));
	$message ->setTo(array($info['email'] => $info['name']));
	
	$message ->setBody('Thanks for entering the competition, we will be in touch if you are a lucky winner.');

	$result = $mailer->send($message);
	
	return $result;
	
}