This feed will add new products and will skip existing products in store that has matching product identifier.
1. On the dashboard, click on the Setup New Feed under the Stock Sync home.
2. Choose an action to perform the Add new products to store. 
3. You will be given an option to Start New or Choose any of the templates provided. In this case, we are choosing to Start New.
4. You can choose any of the connections to import the products, or else can choose the template. A template will be provided with the mapping sections.
5. By default, it will show the upload connection method. You can choose the file format that you want to upload.
6. Click next to go to the field mapping page. On the field mapping, you can assign a product identifier for your products.
7. For the add product feed there is a required field such as SKU, Product's Title, and Price.
8. You can also add any other field that you prefer.
(Please refer here for the Variant Group setting)
9. On the advanced tab, you can choose the auto publish all products with a quantity greater than zero if you do not want to publish any product that is not in stock.
Here is the attached sample file below with the variant group that you use as an example.