I am an owner. How do I delegate permissions on my mailbox to someone else in my organization?

Delegate access can be granted on Outlook for Windows, Outlook for Mac, Outlook on the web, Outlook for iOS, and Outlook for Android. 

You can find more information about how to delegate permissions to someone else here: https://support.office.com/en-us/article/allow-someone-else-to-manage-your-mail-and-calendar-41c40c04-3bd1-4d22-963a-28eafec25926.