Display post of specific category on page

There’s nothing in your code that outputs anything for each post. That’s not what $arr_posts->the_post(); does. You need to use template tags like the_title() and the_content() to output those fields:

while ($arr_posts->have_posts()) {
    $arr_posts->the_post();

    the_title( '<h2>', '</h2>' );
    the_content();
}