How do I configure and sync my WooCommerce products?
Printful ignores products that are marked as "Virtual" or "Downloadable", since Printful can only fulfill tangible products that require a shipping address. These options can be selected both in product and variation settings.
This video goes over how to manually create and sync products from WooCommerce to your Printful account
And this video shows you how to automatically add products using the Printful push generator (accessible from your store's sync page)