Create a new workbook or open an existing workbook.
Click Review > Share Workbook.
On the Editing tab, select the Allow changes by more than one user ... check box.
On the Advanced tab, select the options that you want to use for tracking and updating changes, and then click OK.
If this is a new workbook, type a name in the File name box. Or, if this is an existing workbook, click OK to save the workbook.
If the workbook contains links to other workbooks or documents, verify the links and update any links that are broken.
Click File > Save.
When you're done, - Shared will appear at the top of the Excel window, next to the filename.