If you have access to another account (generic or department account), you can access it by clicking your picture in the top right corner in OWA then choosing Open another mailbox. Type the email address you have access to and the mailbox will open in a new browser tab. If you're using the Outlook program on your computer, you will see the generic mailbox listed in the folder view under your personal mailbox.
If you need to perform a mail merge as a generic email account, you will need to know the passphrase of that account in order to log in directly to that mailbox. Only full generic email accounts that have a passphrase can be logged into directly. Click here to change the passphrase for a generic email account. If you do not know the passphrase to your generic email account, please contact the HelpDesk.
More information on opening and using shared mailboxes can be found at Microsoft online support.