Right click on your calendar and choose “Properties”.
Select the Default entry and change Permission level to the desired setting. If you do not want other people to be able to see subject of your calendar entries, choose “Free/Busy time”.
These are the options:
Permission Level Definition
Owner: Allows full rights to the mailbox (Calendar or Folder) , including assigning permissions; it is recommended not to assign this role to anyone.
Publishing Editor: Create, read, edit, and delete all items; create subfolders. Editor: Create, read, edit, and delete all items.
Publishing Author: Create and read items; create subfolders; edit and delete items created by the user. Author: Create and read items; edit and delete items they’ve created.
Nonediting Author: Create and read items; delete items created by the user.
Reviewer: Read items.
Contributor: Create items.
Free/Busy time, subject, location: View the time, subject, and location of the appointment or meeting on your calendar.
Free/Busy time: Shows only as Free or Busy on your calendar. No details are provided.
None: No permissions are set for the selected user on the specified calendar or folder.