MARKETPRESS - How to use my custom taxonomies with or instead

Hello.

I am having a little trouble with a couple things with the Marketpress plugin.

I am working on a site that currently has a registered custom taxonomy for categories and would like to know how can I use these categories with the product post type?

Also I have an additional custom taxonomy for tags which is used for states. I would like to know how can I use this as well as with marketpress's default tags?