[Plugin: Advanced Custom Fields] Setting arguments for acf_form()

Hey, there! Can you give me an example of how to build my arguments, when building a new acf_form() for new posts? I’m stuck here.

<div id="primary">
		<div id="content" role="main">

			<?php 

			$args = array(
				'post_id' => 'new',
				'field_groups' => array(123)
			);

			acf_form( $args ); 

			?>

		</div><!-- #content -->
	</div><!-- #primary -->

There is acf_head() above as followed. Only appears the button ‘update’. How to call my fields?