In order to add items to the system, you must first add at least one main category, where you can assign the items to.
To create a category...
Click Manage Categories.
Click Create Category.
Enter a Category Name.
Optionally enter a description or image to represent the category.
Set the category to Active.
Enter a sort order, which is the order that the categories will appear.
Click Create Category.
Once you have added the categories needed, you can now add products to your store.