Option 1: Open-/ Libre Office

If you use Open-/ Libre Office as your spreadsheet program, you can easily open a CSV file with these programs. The safest method is to select the CSV file with a right-click, then click on "Open with - Libre Office / Open Office" (Image 1).
When opening the file, "Character Set: Unicode (UTF-8)" should be selected. Confirm your selection with "OK" (Image 2).
Alternatively, you can also open and view the desired CLS file within the running program by clicking on "File - Open..." (Image 3).

Tip: To ensure that the file can subsequently be opened smoothly by Excel users, you can save it as an .xlsx (Excel file) by using "File - Save As...".