Creating a new product page template

  1. From your Shopify admin, go to Online Store > Themes.
  2. Find the theme that you want to edit, and then click Customize.
  3. Open the drop-down menu at the top of the page.
  4. Use the dropdown menu to select a template. Click + Create template.
  5. Give your template a unique name.
  6. Using the dropdown menu, select which existing template you want to base your new template on.
  7. Click Create template.

See Shopify Documentation for more details.