WordPress has some nifty functions which do this for you. You’ll need some experiences with HTML, CSS, PHP to style the output and understand what these functions do but the functions you’re looking for are:
the_date()which displays the post date.the_author()which displays the author of the post.
In your theme will most likely be a page.php template where you can add these on pages into The Loop like so:
<?php if( have_posts() ) : ?>
<?php while( have_posts() ) : the_post(); ?>
<div class="date"><?php the_date(); ?></div>
<div class="author"><?php the_author(); ?></div>
<?php endwhile; ?>
<?php endif; ?>