On Outlook go to 'Calenders', on the left hand side look for the calender you are going to share;
1. On Intel based Mac's with 'Right Click' mouse 'Right Click' on the calender and select 'Sharing Permissions' on Mac's without Right Click mouse use Ctrl + Click.
2. On the 'Permissions' screen you can select whom you wish to share your Calender with and also the 'Permission Level' you wish to give them.
3. Make your selections and simply click 'OK' to save the changes.