After you’ve created a workbook, you need to save it if you want to use it again. Also, if you make changes to a workbook you’ll want to save it. You can even save a copy of an existing workbook with a new name, to a different location, or using a different file type.
Excel normally saves its files as Excel workbooks, but you can save information to other file formats as well. For example, sometimes you may want to save your data as a Comma Separated Values or CSV file, so you can import it into another program.
Click the File tab.
Click Save As.
Click the Save as type list arrow.
The default file type is an XLSX Excel file, but you can choose from plenty of other file formats in this menu.