1. Open and use a shared mailbox in Outlook Desktop Client and Outlook Mobile client

https://support.office.com/en-us/article/open-and-use-a-shared-mailbox-in-outlook-d94a8e9e-21f1-4240-808b-de9c9c088afd

2. Add a shared mailbox to Outlook on the web

https://support.office.com/en-us/article/add-a-shared-mailbox-to-outlook-on-the-web-98b5a90d-4e38-415d-a030-f09a4cd28207

3. Add rules to a shared mailbox

https://support.office.com/en-us/article/add-rules-to-a-shared-mailbox-b0963400-2a51-4c64-afc7-b816d737d164

4. Add the From: line to your email to change to the shared mailbox as sender:

1. Open a new email. Click Options, then Click From:

2. Once you see the From: line, click the down arrow to change the sender: