On Contacts click Import to open the "Importing Data from file" dialog, drag in an .xlsx, .xls or .csv file, tell it which row and column the headers and data start on, then map each KLCT field to a column from your file. Contact Name is the only mandatory mapping; you can also map email, phone, company, job title, website, address, timezone, lead status, interest level, industry type, tags, notes and more. Your mapping is remembered per account for next time.