Use this code in your functions.php
function wpb_change_title_text( $title ){
$screen = get_current_screen();
if ( 'post' == $screen->post_type ) {
$title="Post Title";
}
return $title;
}
add_filter( 'enter_title_here', 'wpb_change_title_text' );
The above code will Place “Post Title
” as placeholder text in dashboard -> posts -> Add New
. Replace that text with your text and also Replace post
with your Post-type.
For more detail read this article