This tutorial is for adding additional mailboxes into the Office 365 Windows version of Outlook. You may need use this tutorial to add a shared functional account which you have been given permissions to access through a -fullaccess or -editor group.
Please note that it will take some time for the servers and system to download emails. If you are adding the account for the first time it will show up on the left window under your main account. You may have to click on the small triangle to expand it.