To pair Joan with Microsoft Office 365, you have to grant Joan the right to manage your Office 365 calendar. There are two ways to delegate calendar access to Joan:
In Office 365, Global Admins are the only role with access to all administrative features. A Global Admin will typically be the person who signs up to purchase Office 365. Your company can also have more than one Global Admin.
Grant Global Admin rights to an Office 365 user by logging into https://portal.office.com with an admin account and go to the "Admin" section.
You can now either create a new account to delegate Global Admin rights to, or delegate admin access to an existing user.
To create a new Office 365 user, go to "Users" > "Active users" in the Office 365 admin center and click on the plus sign. Enter the details of the new user and click "Create." The user will now appear in your list of active users.
To delegate admin rights to an Office 365 user, select a user from the list of active users, go to "Roles," assign the role of "Global admin," and then click "Save."