After you’ve created an option set you need to assign it to product(s) so that options start showing up on the front end.
Steps:
From the Option sets page choose an option set you want to assign.
Within that option set, click on the Products tab.

Now you need to choose one of three ways of selecting products:
Manually - you select the needed products one by one manually or select all the products from the list to assign this option set in bulk.
Automatically - in that case, you can add a condition by which to select products. In this case, both existing products and products added in the future will be assigned with this option set automatically if the condition is met. Currently, the condition could be based on three attributes:
All products - assign the option set to your entire product catalog with a single click.
When this option is selected:
This assignment method is ideal for store-wide options such as gift wrapping, warranties, file uploads, personalization fields, terms and conditions, or rush processing options.
Tick the products you need in the list, one by one. To assign the option set to every product in the list at once, use the checkbox at the top of the list.
Two tabs above the list help you check your work:
Choose this when the products that need the options have something in common — the same vendor, product type or tag. The option set is added to every existing product that matches, and to new products as soon as they match. You don’t need to come back and assign them.
Each field can be used once. To add more vendors, add them to the Vendor condition you already have instead of creating a second one.
Below the conditions you’ll see how many products match and which ones. This list is exactly the set of products that will get the options. If nothing matches, you’ll see No products found — remove a condition or change its values.