On Outlook go to Calendars, on the left hand side look for the calendar you are going to share;

1. On Intel based Macs with Right-Click mouse Right-Click on the Calendar and select “Sharing Permissions” on Macs without Right-Click mouse use [Ctrl] + Click.

2. On the 'Permissions' Screen you can select whom you wish to share your Calendar with and also the 'Permission Level' you wish to give them

3. Make your selections and simply click 'OK' to save the changes.