Legacy Form documentation

Hi, I’m Using Legacy form and want to get first name and a custom text that user inputted and tag the profile based on interest in klaviyo list.

Here is my form:

   <form
    id="email_signup"
    class="klaviyo_styling klaviyo_gdpr_embed_myID email-capture__form"
    action="//manage.kmail-lists.com/subscriptions/subscribe"
    data-ajax-submit="//manage.kmail-lists.com/ajax/subscriptions/subscribe"
    method="GET" 
    target="_blank" novalidate="novalidate">

    <input type="hidden" name="g" value="myID">

    <input class="form-control" id="name" type="text" placeholder="Your Name" data-sb-validations="required" />

    <input class="form-control"  id="k_id_email" type="email" placeholder="Your Email" data-sb-validations="required,email" />

    <input class="form-control" id="customtag" type="text" placeholder="Your Message" data-sb-validations="required" />

    <button type="submit" class="klaviyo_submit_button">Subscribe</button>

    <div class="klaviyo_messages">
        <div class="success_message" style="display:none;"></div>
        <div class="error_message" style="display:none;"></div>
    </div>
</form>


    <script type="text/javascript">
      KlaviyoSubscribe.attachToForms('#email_signup', {
        hide_form_on_success: true,
        extra_properties: {
          $source: 'ContactPage',
          Brand: 'Klaviyo'
        }
      });
    </script>