1. In Outlook for Mac, go to Tools and Accounts. You should see a list of all of your email addresses. Be sure your VCS email account is selected. 

2. Click Delegation and Sharing

3. At top, click Shared With Me then click the plus sign towards the bottom. 

4. In the search field, type the shared mailbox name you'd like to add. Select it and click Add.

5. Click Done. Now when you go back to your inbox, you will see a new folder named after the shared email account. When in the folder, you can compose a new message with the "from" email being the folder/email name.