Add tags to Portfolio – The7

Try below code in your funcions.php to add tags to portfolio post type in The7.2 theme.

add_action( 'init', 'add_tags_portfolio', 0 );

function add_tags_portfolio() 
{

  $labels = array(
    'name' => _x( 'Tags', 'taxonomy general name' ),
    'singular_name' => _x( 'Tag', 'taxonomy singular name' ),
    'search_items' =>  __( 'Search Tags' ),
    'popular_items' => __( 'Popular Tags' ),
    'all_items' => __( 'All Tags' ),
    'parent_item' => null,
    'parent_item_colon' => null,
    'edit_item' => __( 'Edit Tag' ), 
    'update_item' => __( 'Update Tag' ),
    'add_new_item' => __( 'Add New Tag' ),
    'new_item_name' => __( 'New Tag Name' ),
    'separate_items_with_commas' => __( 'Separate tags with commas' ),
    'add_or_remove_items' => __( 'Add or remove tags' ),
    'choose_from_most_used' => __( 'Choose from the most used tags' ),
    'menu_name' => __( 'Tags' ),
  ); 

  register_taxonomy('portfolio-tags','dt_portfolio',array(
    'hierarchical' => false,
    'labels' => $labels,
    'show_ui' => true,
    'update_count_callback' => '_update_post_term_count',
    'query_var' => true,
    'rewrite' => array( 'slug' => 'portfolio-tags' ),
  ));
}

function add_portfolio_tags_after_post($content){
if (is_single() && 'dt_portfolio' == get_post_type() ) {

	$tags = get_the_term_list( get_the_ID(), 'portfolio-tags', '', '', '');	
	$content .= '<div class="entry-tags">'.$tags.'</div>';
}
	return $content;
}

add_filter( "the_content", "add_portfolio_tags_after_post" );

You may need to reset permalinks after adding the code.