Do you want to send a email to the customer or yourself? You can add some kinda easy code to send an email to yourself.. I think something like this should work:
define(EMAIL_TEXT_SUBJECT,'A product got sold');
$email = "Hello admin.. "\n\n";
$email .= "Your product: ".$product_info['products_name'].' got sold"\n\n";
$email .= "More info here.."\n\n";
$email .= "more info here.."\n\n";
$email .= "And so on...";
tep_mail(STORE_OWNER, STORE_OWNER_EMAIL_ADDRESS, EMAIL_TEXT_SUBJECT, STORE_OWNER.' '.STORE_OWNER,STORE_OWNER_EMAIL_ADDRESS);
If it works you can place it on checkout_success and every time someone order something you will get an email..