filtered portfolio

I want to create a portfolio page that only features only that work in a certain category. So instead of going to a page that features thumbnails of all of the portfolio I only want that page to feature some of the portfolio. So I created a page, gave it a Parent for the main Portfolio page (that does feature the entire portfolio, and applied the Portfolio template. But then what do I do to only get portfolio items of a certain category to show up on that page?