Thank you for your inquiry, you will need to upload the file in .csv format, also to ensure that the server is able to support the upload, ensure cURL library is turn on. You can test this by uploading the sample csv provided in the import/export page.
If that file is able to import, you may need to edit the file using notepad and ensure the formatting (comma, quotes) are exactly the same with the sample to make the import is successful.