First of all, add Teams, Positions, Working Weeks, Approval Flows, and Holiday Calendars to your Calamari account. Upper case letters makes difference!
Download and fill in the template file
Make sure that the dates (hire date, birth date) have the same format as the date in your Calamari account
Please check if there are no empty spaces left at the end of each line
Format everything as text
Make sure there is no string delimiter
Save the file as a CSV format
Log in to Calamari → go to Configuration → Import → Employee import → and upload your file :)