To save an Excel workbook in MS Excel 2010, you can use the keyboard shortcut Ctrl+S. This shortcut saves an existing workbook in its current location. If you need to save your workbook for the first time, in a different location, or to create a copy of your workbook in the same or another location, you need to use the Save As command. To use the Save As command, you can follow these steps:

1. Open the workbook you want to save.
2. Click the File tab.
3. Click Save As.
4. Pick the place where you want to save your workbook.
5. Enter a name for your workbook in the File name box.
6. To save your workbook in a different file format, pick the format you want in the Save as type list.
7. Click Save.

Alternatively, you can use the keyboard shortcut Alt+F+A to open the Save As dialog box.