Protecting a Taxonomy Term of any type (for example, Category or Tag) protects Permalinks leading to Posts associated with that Term.
For instance, if you protect a Tag, WooCommerce Restrictions protects all new and existing Posts assigned that Tag automatically. The same principle applies to Posts in a protected Category including Child Categories of a Parent Category that you have protected.
This is where you create new Restrictions. There is a meta box here called Protected Categories/Tags where you protect content assigned particular Categories and Tags.
You can start typing in a name or just click in this box to see the list of Taxonomy Terms attached to Posts of any kind. Select the Term or Terms you want to protect with this restriction from the drop-down list.
When you have finished creating Restrictions, click the Create Restriction button at the top-right of the page.