This screencast expands the simple import we did before using Commerce Feeds. Here we add an attribute to the product, and then import multivalued product reference fields on the node. The manual page that goes with this is http://www.drupalcommerce.org/user-guide/importing-products-using-feeds . If you haven't already you may want to watch the introductory importing screencast at http://vimeo.com/22731881 .

We're going to add an attribute for our new product. Make sure you click "This field is a product attribute" checkbox when adding a text (list) field.