Add Categories In Search Results

I have a 1st level (root) category called "clothes" and a 2nd level category under that called "pants". However, is someone searches for "clothes" or "pants" no results appear, unless the specific words are included in the product's name or SEO keywords. How can I make the search results include all products under a specific category, when someone searches by the name of the category?

You can only put category name to the search words field. It can be easily done with export/import feature