If you want to share a workbook and allow changes by more than one user at the same time you need just to go under the REVIEW panel press the Share Workbook icon and tick the box under editing.
To allow this file to be protect by an encrypt password you need to change some settings under Options —- Trust Center —- Trust Center Settings —- Privacy Options —- and make sure that is unchecked the box that says ” Remove personal information from file properties on save”