For Outlook Client:
The email will appear in your Outlook client on the left, below your Inbox. (this may take an hour or so to appear). If you are using the New Outlook the mailbox will be under "Shared With Me" folder.

For Browser access:
a. From your Web Outlook, click your initials in the top right. (If you have a picture associated with your account, click the picture)
b. Select “Open another mailbox”
c. Type mailbox name and select the email from the list. Then click Open.
d. The Mailbox will open in a new tab. Bookmark that page.
To open the shared mailbox in the future, go to that bookmark.