Displaying Post Navigation for Custom Post Types

By default, the post navigation option in the customizer only works for Posts post type. The following PHP snippet can be used to enable it in your CPT as well:

add_action( 'generate_after_entry_content', 'tu_cpt_footer_meta' );
function tu_cpt_footer_meta() {
    if ( is_singular( 'your-post-type' ) ) : ?>
        <footer class="entry-meta">
            <?php generate_entry_meta(); ?>
            <?php generate_content_nav( 'nav-below' ); ?>
        </footer><!-- .entry-meta -->
    <?php endif;

Learn how to add PHP here.

Make sure to replace your-post-type with the name of your CPT.