To import a shopping cart, simply click on this symbol (top right) next to the shopping cart and then "IMPORT SHOPPING CART". Click the green "SELECT FILE" button and select a suitable .csv file that does not exceed 10 kb. Furthermore, the file should contain the product SKU and the product quantity exactly in this order. Click the green "IMPORT" button. Now you can retrieve your saved shopping cart. 

In the blue box, there is a link to the imported, saved shopping cart. Alternatively, you can click on "MY ACCOUNT" above the shopping cart and on the menu item "SAVED SHOPPING CARTS" to go to your imported cart. You can now restore your shopping cart so that your current one updates to the saved one.