Add a shared account as a folder in new Outlook
Right click on your account name or email address
Add shared folder or mailbox
Type an email address or name of the account you want to add > click Continue
When added, restart New Outlook
Added account will be accessible in Shared with me folder
Or
Go to File > Settings > Shared with me > Add
Type an email address or name of the account you want to add > click Continue
When added, restart New Outlook
Added account will be accessible in Shared with me folder