To save a spreadsheet as a CSV in Excel, go to File > Save as and select CSV as the file type. In Google Sheets, go to File > Download, then select Comma Separated Values (.csv).
Open the workbook you want to save. Pick the place where you want to save the workbook. In the Save As dialog box, navigate to the location you want. Click the arrow in the Save as type box and pick the type of text or CSV file format you want.