In this guide, we explain how to add a member to a shared mailbox.
Go to 'Teams and groups' -> 'Shared mailboxes'.
Open the shared mailbox to which a member should be added.
Click on 'Members' -> 'Edit' under the mailbox details.
Click on 'Add members'.
Select the user(s) to be added by checking the box next to their name and clicking on 'Add'.
It may take up to one hour for the member to be fully added to this mailbox.