Hi Ginnie,
There are two ways you can do this. One is with the templates from the template builder and the other is using the Theme Options>Portfolio and creating a new set of portfolio options for each category page you want to display. Just click on the little green + and it will create a new set of options and then you designate the page for the content to appear on and what categories to show on that page.
Just make sure that you delete any option groups that don't have a page set with the dropdown as that tends to cause some odd issues. You can remove a group by clicking on the red X on the bottom right of that group.
Regards,
Devin