An attribute makes its options available to products. It does not create variants or a storefront filter by itself.
Use options on a variable product
Open Catalog > Products and create or edit a variable product.
Under Variant options, select the attributes that define the choices customers can buy. On a new product, choose Generate variants; on an existing product, choose Add combinations for new choices.
Keep only the combinations you sell, then review each variant's SKU, prices and inventory before saving.
Adding an option to an attribute later does not add a variant to products already using it. Open each affected product and add the combinations you want to sell.
Offer a storefront filter
In Store Admin, open Catalog > Filters and select Add filter. Choose Attribute as the source, select the attribute, review the filter and display choices, then create the filter. A saved filter is separate from the attribute and can be removed without deleting the attribute.
A variable product can use up to 3 driving attributes, and an attribute can have up to 100 options. See Product limits for the variant ceiling.