Adding a list with products

How do I add a list with products in Billit?

To add a product list, first click 'Download empty excel list' in the ‘Product’ menu.  If you already have a list and want to add products to it, click on the 'Export' button.
An excel file will now download to your computer. Fill it in (or copy and paste the data from a different document) and import the list again in Billit by clicking ‘Import’ and selecting the completed file from your computer.

How do I import an excel list with products?