WordPress Theme Folder Structure:

Video

Custom Page Template:

<?php
/*
* Template Name: My Page
*/

get_header();
echo "<div><h1> Demo of My Page</h1></div>";

while (have_posts()){
	the_post();
	echo "<div>This is demo of My Page</div>";
	the_title();
	the_content();
}
dynamic_sidebar("test-sidebar");
get_sidebar();
get_footer();