Once you've saved your Product listing, you'll move on to create your SKUs. If you're in the process of creating a new product listing, you'll be led to the SKUs page; from there, click "add SKU". You'll create a new SKU for each new size, quantity, color, etc. you offer for this product.
If you have already saved your product / SKU and want to edit the SKU, click "edit SKU" from the Product page.
The attribute is used to describe the size, quantity, color etc. For example, this can be "8 oz jar", or "box of 6" or "color: red".
The SKU ID is a short code the identifies the SKU for order tracking purposes.
For example, your 8 oz jar of eucalyptus honey could be: "honey_eucalyptus_8oz", or better yet, "HE8OZ".
Unit Shipping (SKU shipping):
Shipping prices are calculated as the sum of the Base Shipping plus the Unit Shipping. The Unit Shipping is applied once per item ordered. This allows you to set up different shipping prices according to your needs. See "Setting Your Shipping Prices" below.