This feature is based on uploading a CSV file from your e-mail client. What does this mean? In short, we tell you how can you save your addressbook in Outlook or Thunderbird as a file with e-mails separated by semicolons.
Once that's done, we explain how to send this file to us, so that we can give you a list of all your contacts to choose from. Just follow the instructions on the right - we made the process as easy as possible for you, so there's nothing to worry about.