Resolution:  

1) Launch Microsoft Outlook and click on the "Calendar" button located on the bottom left of your screen. 

2) Select the calendar you want to edit in the bottom-left column by performing a right-click and then choosing "Properties".

3) This will open up the "Calendar Properties" window. From here, you can select the "Permissions" tab on the top.

4) Now you will have the options to Add users from the global address list that you would like to be able to view your calendar, and set their desired Permission level. 

5) When you are finished, you simply select "Apply" and then "OK" to complete the changes.