How to use my custom sign up form

Greetings,

The plugin seems to be working great so far, no issues there.

My problem is that I need to use a custom form provided by my theme for sign ups. I can call this form via shortcode, and it fits in perfectly with my theme.

I'm just not sure how to make it work with this plugin though. Here's the code I found for the form I would like to use:

function newsletter_form_func($atts, $content = null) {
   	extract(shortcode_atts(array(
      	"action" => '',
      	"label" => '',
      	"label_submit" => __( 'Sign up', TEXTDOMAIN ),
   	), $atts));

   	$html = '
<form method="post" action="' . $action . '" class="newsletter-form">
	<fieldset>
		<label>
			<span>' . $label . '</span>
			<input type="text" class="email-newsletter" name="email-newsletter" />&nbsp;
		</label>
		<input type="submit" value="' . $label_submit . '" class="subscribe-newsletter" name="subscribe" />
	</fieldset>
</form>'; 

	return apply_filters( 'yiw_newsletter_form_shortcode', $html );
}
add_shortcode("newsletter_form", "newsletter_form_func");

What do I need to do to make my form work with your plugin? Any help is greatly appreciated!

Thanks!