Sign in to your account in Outlook on the web. Login to https://www.outlook.com, then click on Outlook.
On the Outlook on the web navigation bar, select your name in the upper right corner.
Choose Open another mailbox.
Enter the email address of the shared mailbox that you want to access and select Open.
Another Outlook on the web session opens in a separate window, allowing access to the shared mailbox.
Select the Settings menu icon and choose View All Outlook Settings.
From here, you can create Rules, Automatice Replies, Forwarding and more.