In order to classify your categories, you will need to first install the Classify Categories and Products feature within your online shop. Do this by going to the Features section of your EKM account.
Once installed, you can select from within the feature whether you want to use Google's classifications, or eBay's classifications (or select both).
Once you have the feature set up, you will then see the Classification tab when editing a product or category. Here you will be able to classify the product or category.
To expand a classification category, simply click the white arrow next to the to level category and repeat the process until you have reached the correct classification category.