I have searched this forum and Excel help and cannot find the answer to my
seemingly simple question.

How does a user take a file out of exclusive use?

We have an Excel file that was shared and the user accidently put the file
in exclusive use mode, now we are unable to share the file again.

The user does not know how she put the file in exclusive use, can anyone
tell me how this is done?

Any help will be much appreciated.