Storefront Mega Menus allows you to create enhanced full-width dropdowns that seamlessly integrate with your Storefront-powered WooCommerce shop.
Download the .zip file from your WooCommerce account.
Go to: WordPress Admin > Plugins > Add New to upload the file you downloaded.
Activate the extension.
Click Save Changes.
Storefront Mega Menus adds all its settings to WordPress Customizer, making it straightforward to use. Upon opening the Customizer at Appearance > Customize, navigate to Menus.