I was going through the steps you provide in the Help and Support and walking through the demo. On the topic of adding SKUs to products, you give the following instructions:
After adding a product, to add its variants:
1. Login to the storefront administration website. The Storefront Dashboard page is displayed.
2. On the left Navigation pane, click Products under Catalog. The Products page is displayed.
3. Click Manage on the product for which you want to add SKUs. The Product Details page is displayed.
4. Click Manage SKUs tab and then click on Add SKU or Part #. The Add Product SKU page is displayed.
However, when you go to the demo and walk through that process, there is no 'Manage SKU's' tab on the Product Details page.