Used to do the next to show just one publish during my webpage:

home.php:

<?php
get_header();
query_posts('posts_per_page=1'); //returns only the front page
?>

<div id="content">
    <?php
    /* Run the loop to output the posts.
     * If you want to overload this in a child theme then include a file
     * called loop-index.php and that will be used instead.
     */
    get_template_part( 'loop', 'index' );
    ?>
</div>
<div id="sidebar">
    <?php get_sidebar(); ?>
</div>
<div id="footer">
<?php get_footer(); ?>

However I still ahave to click Comments to be able to begin to see the comments and also the form to depart a comment. How do i instantly show immediately?

Load your comments ought to template using <?php comments_template(); ?> - that'll display all comments for that current publish.