Like most WooCommerce extensions, you can find the global settings within WooCommerce->Settings->Product Sample.
Configure it globally, and done.
You can also configure product samples on a per-product level.
This option is helpful if you only want to provide product samples for specific products in your store.
Product Sample automatically uses the styling from your theme and does not include any additional styles.
This ensures maximum performance and eliminates any theme-incompatibilities.