A shared mailbox is an inbox that allows multiple people to send and receive email from the same address. For example, if you have a public-facing email address and multiple people need to read the incoming mail, a shared mailbox would be the right solution.
The IT Department creates and administrates shared mailboxes, so if you need one set up or if you need people added or removed from the mailbox, you will need to submit a support ticket (simply email firstname.lastname@example.org or create a ticket through the Support Site at https://support.roundrocktexas.gov).
If you have access to a shared mailbox, you will see it in your Outlook Mailbox as a separate inbox on the left side navigation pane, as shown below:
Click the arrow to the left of the mailbox name to expand the folders within that mailbox.
If you have permission, you can send email from the shared mailbox email. You may have access to a shared mailbox but only be able to send email as yourself instead of the mailbox address. Contact IT if you have questions regarding this setup.