How to show featured image inside post

review: https://codex.www.ads-software.com/Post_Thumbnails

i have added this code

if ( function_exists( 'add_theme_support' ) ) {
  add_theme_support( 'post-thumbnails' );
}

but what should i add in single.php

i have wordpress 3.3.1 and fresh news theme installed

i did it earlier with the same theme but i have forgotten
please help me

Set the default Post Thumbnail dimensions with: https://codex.www.ads-software.com/Function_Reference/set_post_thumbnail_size
and in your single.php put this just above <?php the_content(); ?>:

<?php
if ( has_post_thumbnail() ) { // check if the post has a Post Thumbnail assigned to it.
  the_post_thumbnail();
}
?>

see: https://codex.www.ads-software.com/Function_Reference/the_post_thumbnail

what theme are you using (link please)?

@keesiemeijer

i have done it and with you help onky
THANK YOU !!

You’re welcome. Im glad you got it resolved.