"My understanding of this question is that you have a Spreadsheet (XLS) that you want to save as a CSV to export the data to another system.
Choose File > Save As...
In the Type drop-down list, select Microsoft Excel Workbook (XLS)
However, on reading it again it appears you may want to open a CSV file, and then save it as an XLS. choose Data > Import External Data > Import Data choose Text file in the drop-down list."