In order to give your listings storefront template via bulk, you will need to add header type to your bulk upload:
The value of your template can be found in Tools>Templates>*your template name.
That is the folder where all your storefront files are positioned.
The default template of your listings is product.htm that can be converted as value under the header type as "product".
Template file Bulk value
After you set up your CSV, you can submit the upload. Please remember you can skip all channels on the upload that way it processes faster!