You can go to this page, or follow the instructions below.

1. Open your browser and navigate to https://outlook.office.com.

2. In the top right corner, select your profile.

3. In the menu that opens, select 'Open another mailbox'. A popup will appear.

4. Enter the full email address of the shared mailbox you are trying to access.

5. The mailbox will open in a separate tab. Click on the settings cog icon on the top right toolbar. At the bottom of the settings pop-out menu, click ‘View all Outlook settings’.

6. Make sure you are in the Email menu to the left of the pop-up window. Then click ‘Automatic replies’ on the secondary menu. Here you can switch on automatic replies, set time frames, and write internal and external automatic replies.

7. Hit 'Save' when you are done.