Please follow these step by step instructions to easily add / edit the SKUs of your product:
- From your Shopify admin https://yourwebsite.myshopify.com/admin, go to Products (or simply go to https://yourwebsite.myshopify.com/admin/products)
- Click All Products
- Click the "Square box" filter right below "Filter Products" to Select All Products
- Click Edit products
- Add/Modify the SKU for each product and click "Save"
Note: Product SKUs need to unique (different) across all listings. For variant products, the SKU for each variant option has to be different.