How to make blog post entries appear as input form instead of just text?

You probably want this:

<form action="demo_form.php">
  <textarea name="blogpost" readonly="readonly">
    <?php the_content(); ?>
  </textarea>
  <input type="submit" value="Submit">
</form> 

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)