There are two main steps to adding categories to your auction items: creating your categories and assigning categories to items.
Create your categories
From your Event Dashboard, click Auction Settings
Click Add Category and enter your category name.
Assign categories to items
Find your auction items in your Event Dashboard.
Click the pencil icon in the lower right hand corner of an auction item.
Select a category.
When bidders browse items on your Auction Site, they'll be able to filter by category.