I tried something like this
function acf_set_featured_image( $value, $post_id, $field ){
if (is_user_logged_in()) {
if($value != ''){
//Add the value which is the image ID to the _thumbnail_id meta data for the current post
add_post_meta($post_id, '_thumbnail_id', $value);
}
return $value;
}
}
add_filter('acf/update_value/name=main_image_logged', 'acf_set_featured_image', 10, 3);
but its wrong