$title = get_the_title();
$args = array('posts_per_page' => -1, 'post_type' => 'post');
$posts = new WP_Query($args);
foreach($posts as $post){
update_post_meta($post->ID, '_yoast_wpseo_focuskw', $title);
}
wp_reset_postdata();
this is a sample code like this create a loop that loops through all the post and then update the post meta
and after that create a blank page that doesnt contain a loop and add this code in it
$posts_query = new WP_Query(
array(
'post_type' => 'post',
'posts_per_page' => -1
)
);
while($posts_query->have_posts()) : $posts_query->the_post();
$title = get_the_title();
$post_id = get_the_ID();
update_post_meta($post_id, '_yoast_wpseo_focuskw', $title);
echo $title . ' Meta Updated<br />';
endwhile;
after that create a page using this page template