How to share an Outlook calendar and set permissions

To share the calendar open Outlook and click on Calendar and the Home tab.  Then click Share Calendar

The Calendar Properties box will pop up; on the Permissions tab click the Add button and then select the user who you'd like to share your calendar with. Once their name is at the bottom, click OK.

In the Permissions section underneath, select the type of access you want the user to have - in the below example I have selected 'Can view all details' but you may want to allow change that to 'Can edit' if you would like someone else to manage your Calendar

Click Apply and this will send an email to the person you are sharing the calendar with.  The other user will receive an email inviting them to view the calendar – they need to click the Accept button in the top corner: