functions.php
        wp_enqueue_style( 'style-name', get_stylesheet_uri() );
	wp_enqueue_style( 'style-boot', get_template_directory_uri() . '/assets/css/bootstrap.min.css' );
	wp_enqueue_script( 'script-name', get_template_directory_uri() . '/assets/js/bootstrap.bundle.min.js', array(), '1.0.0', true );

         add_theme_support( 'title-tag' );
         add_theme_support( 'custom-logo');
         add_theme_support( 'post-thumbnails' );

         register_nav_menus(['TM'=>'Top Menu','FM'=>'Footer Menu','list'=>'List']);

       register_sidebar([
	      'name'=>'Sidebar Image',
	      'id'=>'side_img_1',
	      'before_widget'=>'',
	      'after_widget'=>''
       ]);

index.php
            <?php wp_head(); ?> 
            <?php wp_footer(); ?> 

            <?php the_custom_logo(); ?>

           <?php 
                  wp_nav_menu([
                  'theme_location'=>'TM',
                  'menu_class'=>'navbar-nav1 l-items',]);
                ?>

            <?php while(have_posts()){the_post() ?>
                  <div class="carousel-item active">
                    
                    <?php the_post_thumbnail([660,300]) ?>
                   
                  </div>
                  <?php } ?>

 style.css
       .l-items{
                   list-style: none;
                   display: flex;
        }
      .l-items li a{
               text-decoration: none;
               padding-right: 10px;
               margin-right: 10px;
               border-right: 1px solid gray;
    
        }