Your import file must be in comma-separated values format (or CSV for short). If you have your list of customers saved as a Microsoft Excel spreadsheet then it's easy to convert that file to a .CSV file. Here's how:

1. Open your list of customers in Microsoft Excel
2. Depending on which version of Excel you're running, either click the Save As option under the File menu or click the Office button and then move your mouse over the Save As menu and choose the Other Formats option.
3. When the Save As dialog box appears choose CSV (Comma delimited) (*.csv) from the Save as type pulldown menu.
4. Type a name for the file into the File name field, such as customers.csv and click Save