Register a Custom Post Type

function my_register_portfolio() {
    register_post_type( 'portfolio', array(
        'labels'       => array(
            'name'          => 'Portfolio',
            'singular_name' => 'Project',
        ),
        'public'       => true,
        'has_archive'  => true,
        'menu_icon'    => 'dashicons-portfolio',
        'supports'     => array( 'title', 'editor', 'thumbnail' ),
        'show_in_rest' => true,
    ) );
}
add_action( 'init', 'my_register_portfolio' );