To assign a password to an Excel workbook, do the following: 1  From the File menu, choose Save As. 2  In Excel 2007, click the Office button and choose Save As. 3  In 2010, click the File tab and choose Save As.4  Click the Tools dropdown on the dialog toolbar and choose Save Options. In Excel 2007, click the Office button and choose Save As. 2  In 2010, click the File tab and choose Save As. 3  Click the Tools dropdown on the dialog toolbar and choose Save Options. 4  In Excel 2007 and 2010, click the Tools dropdown (in the bottom left corner of the dialog box).