“Dashicons” is the official icon font of the WordPress admin as of 3.8.

Please find below link to check dashboard icons to use and change.

Goto Dashboard icons

Use below code to set icons for wordpress custom post types.

Use below code in functions.php

function wpdocs_create_post_type() {
register_post_type( ‘acme_product’,
array(
‘labels’ => array(
‘name’ => __( ‘Products’, ‘textdomain’ ),
‘singular_name’ => __( ‘Product’, ‘textdomain’ )
),
‘public’ => true,
‘has_archive’ => true,
‘menu_icon’ => ‘dashicons-products’, // Here change Icon
)
);
}
add_action( ‘init’, ‘wpdocs_create_post_type’ );