A properly formed CSV file should be selected on your computer HDD. It must contain the fields or columns separated by a delimiter which will be used to import persons or companies - 'First Name' and 'Last Name' for persons, 'Company Name' for companies. The files containing more than {0} rows should be divided into smaller parts for proper importing. Make sure you selected the portal users who need to be granted access to the contact details, otherwise the data from the CSV file will be available to you only.