Need 2 templates for pages: full-widh & with-right-sidebar

I would like change an old theme “gold” that i installed 12 years ago for company page https://computers-and-control.pl.

Theme Melos would be nearly OK for this and i created test-page on https://computersandcontrol.pl.

The main problem is that i have and i need some pages with template with right-sidebar and other pages with template full-width.

I try create template ccfullwidth.php and content-ccfullwidth.php files but I have no idea what else add or change in database probably in wp_options table ( I use phpmyadmin) to get new/second page template?

ccfullwidth.php file:

       <?php
/**
*
Template Name: CCfullwidth
*
 */

get_header(); ?>


             <?php while ( have_posts() ) : the_post(); ?>

                            <?php get_template_part( 'content', 'ccfullwidth' ); ?>




                            <?php /* Add comments */ thinkup_input_allowcomments(); ?>

                    <?php endwhile; wp_reset_postdata(); ?>



<?php get_footer(); ?>

content-ccfullwidth.php file:

<?php
/**
 * The CCfullwidth  content template file.
 *
 * @package ThinkUpThemes
 */
?>




                <article id="post-<?php the_ID(); ?>" <?php post_class(); ?>>


                <?php wp_link_pages( array( 'before' => '<div class="page-links">' . __( 'Pages:', 'melos' ), 'after'  => '</div>', ) ); ?>

                <?php the_content(); ?>

                </article>

The page I need help with: [log in to see the link]