To upload data to it is necessary that it is in the *.CSV format. You can save any spreadsheet as a *.CSV file.
With macOS devices you are required to Export to a *.CSV file. This can be found under File in the menu bar.
You can tell if it is in the correct format if the ending is .csv
For Windows, you can save it as a *.CSV file. Select this option from the File Format drop-down.