By default, all products are assigned to the Default product template. Assign a product to an alternative template through the Products admin.
For single products, use the Theme templates portion of the product editor.
To apply a particular template to multiple products at once, use the Bulk editor.
Batch-assign a template to products
- Open Products in your Shopify admin
- Use the checkboxes beside each product to select the products for the template

- Select Edit products

- In the Bulk editor, select Add fields then Template

- Use the new column for Template to adjust each product

- Once all the products have the template adjusted, click Save