Open an option set and click the choice field in the preview (or start from the swatch template in Help).
Under Choices, give each choice a Color or an Image link. A choice with neither shows as a button with its name.
To let shoppers choose more than one, turn on Shoppers can pick several.
Under Products, choose where it shows, then click Save.
Still stuck?
Open the app in your Shopify admin, go to Help and click Chat with us, or email [email protected] with your store’s myshopify.com address.