Close all instances of Outlook.
Follow the guide at Create an Outlook profile - Microsoft Support and at step 3 click "Prompt for a profile to be used" before selecting New which will provide a prompt when opening Outlook. Alternatively press and hold the Shift key when opening Outlook to move between different Outlook profiles.
At step 5, enter the shared mailbox email address and click on connect.
Click on “Sign in with another account”.
Change the email address to your RGU email, click Next and enter your password.
Click Done and click OK on the Choose Profile box.
RGU IT and Digital
Service Catalog Portal: Support : IT Service Desk (freshservice.com)
https://itservicedesk.rgu.ac.uk
Tel: 01224 262777