Office 365 (Outlook 2013 / 2016 / 2019 for Win) - Manage Another Person's Calendar and/or Email (Act as a Delegate)
For the most current information on managing another person's calendar and/or email in Outlook, please reference the following Microsoft support article: https://support.office.com/en-us/article/manage-another-person-s-mail-and-calendar-items-afb79d6b-2967-43b9-a944-a6b953190af5.
Note: The procedures in this article assume that someone has already granted you Delegate Access permissions. For more information on those steps, please see Office 365 (Outlook Client for Windows) - Allow Someone to Manage Your Calendar and/or Email (Assign a Delegate) .