Note: To add a feature to your product, first you must have features setup in your store.
To attach a feature to your product go to Products > View Products menu. Once clicked on this will display all products available in your store.
To edit a product click on the "pencil icon" next to the product.
The product screen is split into tabbed sections: General, Specifics, Connect, Features, Variants, Images, Promotions, SEO. Click on the tab called "Connect".
In this section you will be able to add your feature to your product.