Outlook: Calendar Permissions
Select Calendar from the Navigation Pane at the bottom of the Folder Pane.
Or Compact View
On the toolbar, select the Calendar Permissions option.
The Calendar Properties dialogue box opens. Select the Permissions tab.
The current list of those with access to the calendar and their permission level will be displayed. The options can be updated by selecting their name and then changing the permission level.
Once the permission level is adjusted, click OK.