components/forms/14-field-set/field-set.html

<fieldset class="mzp-c-field-set">
  <legend class="mzp-c-form-subheading">Legend</legend>
  {% render '@input-field', { type: 'text', label: 'Field one', id: 'one', name: 'one' } %}
  {% render '@input-field', { type: 'text', label: 'Field two', id: 'two', name: 'two' } %}
  <p class="mzp-c-field-set-info">Additional info about this field set.</p>
</fieldset>