A category page shows every product that carries its tag.

PUT A PRODUCT IN A CATEGORY

Add the category's tag to the product (Tags, in the product's Settings). A product can be in two categories: give it both tags.

CREATE A CATEGORY

Your theme comes with category pages. Find them in Ecommerce → CATEGORIES. Click the clone icon on the one you like, then change its Page Name and Page URL and click SAVE. Open it with EDIT, click the product listing and set its Tags to your new category's tag.

MY CATEGORY PAGE IS EMPTY

No product carries the tag the listing shows, or the tag is spelt differently. Check the tag on the listing and on your products.

CATEGORIES IN YOUR MENU

The Category menu shows what you add to it in Navigation, not your tags. Add your category pages there.

To hide a category for now, set its Page Status to Draft.