First you choose your file (either .xlsx or .csv). Then you choose a worksheet and select the columns that should go on the front side and those that should go on the back. You decide the page size and how many flashcards should appear in a page. After that you can print the pages with your flashcards to a PDF file or print directly through your printer.
FrontBackPrint works on macOS, Windows, and Linux. If you purchase the app for $15, you get to download all versions.