Add a shared calendar to Outlook
You may have access to a shared calendar, or maybe a colleague has shared their calendar with you. To access that calendar in Outlook, follow the steps below.
In Outlook, click the Calendar button.
In the ribbon at the top, click + Add Calendar (or just + Add depending on your Outlook view) and then click Open Shared Calendar.
Type a name in the Name box, or click Name to select a name from the Global Address List.
The shared calendar appears next to your existing calendar.
After you access a shared calendar for the first time in this way, the calendar is listed in the left-hand folder pane in Outlook. The next time that you want to view the shared calendar, you can click it in the folder pane rather than repeating this process.
You can overlay the calendars to make them appear on top of each other by clicking ← in the top-left of each calendar, and then then switch back to side-by-side mode by clicking →