This script demonstrates how to add delegates in Office 365 Exchange Online. You can add delegates for multiple users.
Currently, you can easily add delegates in Outlook. However, you cannot add delegates in Outlook Web App (OWA). If you only use OWA, a workaround is needed to mitigate this problem.
You can find more All-In-One Script Framework script samples at https://aka.ms/onescriptingallery