Okay. Well, to start with, you can hide that link with CSS (target the class taf-anchor).
Then, you'll need to have your link fire some JavaScript when it is clicked, so that it calls the modal method of the form (which has the CSS class taf-form-wrap). That could look something like this:
<a href="#" class="friends-link">Tell Your Friends!</a>
<script type="text/javascript">
(function ($) {
$(function () {
$('.friends-link').click(function (evt) {
evt.preventDefault();
$('.taf-form-wrap').modal({ persist: true });
});
});
})(jQuery);
</script>
Hope that helps,