In order to translate theme's text strings to a language different than English, you have to use Loco translate.
This process give you the ability to have a shop in a single language. In order to have a multilingual shop, you need to use WPML (premium plugin, sold separately).
After installing Loco translate you can find the theme's text strings under Loco translate > Themes.
Check out this video for an example on how to translate the 'No products in cart' string in the drop-down shopping cart:
Hint: If you are having trouble translating the drop-down Cart's contents, try changing the items included in the cart, by adding/removing a product, in order to clear the internal WooCommerce cart cache.