You have two options for listing your data to the webstore
Option #1 - User Interface
This is a great option for most cases. We recommend using this for anything less than 100 products at a time. In fact, it can be a great option for listing almost any amount of products. Everything is highlight, point, click. For detailed instructions, Click Here
Option #2 - Import csv File
Great for listing products in bulk. The csv file allows you to easily visualize all of your catalog data and the categories that your are trying to map to. For detailed instructions, Click Here