Basic marking for creating a standard subscribe form looks the following way:

<form data-form-output="form-output-global", action=' url ' method='post' class="rd-mailform form-inline">   <div class="form-group">     <label for="contact-email" class="form-label">E-Mail</label>     <input id="contact-email" type="email" name="email" data-constraints="@Email @Required" class="form-input">   </div>    <button type="submit" class="button button-primary">Send</button> </form>