How to Save a Spreadsheet as a CSV file
Product lists contained within spreadsheets must be saved in the CSV format (Comma Separated Values) before they can be imported. This is easily done in most spreadsheet products, such as Microsoft Excel.
In Microsoft Excel, simply click on the File menu at the top of the toolbar and select Save As.
Underneath the File Name box, you are able to select a File Type from a dropdown list. Select CSV (.csv) from that dropdown menu, enter a name for the file and then click OK. If you are presented with a confirmation box, simply click Yes.