Click on the button in the navigation.
Choose a product whose settings you want to duplicate.
Select the products you want to copy the product option settings to.
Click the button.
The options will only duplicate to products selected on the current page.
You can also set up default option settings for all products. Read this article for more information.
If you are using Shopify Options, the values of these options won’t be duplicated with this tool. Read this article for more information.