This Version is Out of Date
You can find the updated Miva 10 Reference Guide here
Use the Edit Product > Categories tab to add your products to existing categories and to create new ones. You can also do both of these activities from the > Categories screen.
The Categories tab shows all of your current categories. Click the Assigned icon next to a category to make it turn blue. The product you are editing will be listed in that category in your on-line store.