source: http://docs.buddyforms.com/article/309-create-custom-general-settings-tab-for-your-extension

buddyforms_settings_page_tab.php

<?php

//
// Add the Tab Content
//
add_action( 'buddyforms_settings_page_tab', 'my_buddyforms_settings_page_tab' );
function my_buddyforms_settings_page_tab(){
  ?>
<div class="metabox-holder">
  <div class="postbox">
    <h3><span><?php _e( 'LABEL', 'buddyforms' ); ?></span></h3>
    <div class="inside">
      <p><?php _e( 'DESCRIPTION' ); ?></p>
      <form method="post" enctype="multipart/form-data">
        <p>
          // Form Fields
        </p>
        <p>
          <?php wp_nonce_field( 'buddyforms_INPUT_nonce', 'buddyforms_INPUT_nonce' ); ?>
          <?php submit_button( __( 'Submit' ), 'secondary', 'submit', false ); ?>
        </p>
      </form>
    </div><!-- .inside -->
  </div><!-- .postbox -->
  </div><!-- .metabox-holder -->
<?php 
}

//
// Add the Tab Navigation Item
//
add_filter( 'buddyforms_admin_tabs', 'my_buddyforms_admin_tabs' );
function my_buddyforms_admin_tabs($tabs){
  $tabs['TAB SLUG'] = 'TAB LABEL'; 
  return $tabs;
}