Go to outlook.com and log in.
Once logged in, go to your icon in the upper-right-hand corner and select "Open another mailbox"
In the dialog box, type in the mailbox you'd like to view (ex: help@alcsolutions.com). It may try to auto-complete what you're typing.
Select open and the page should refresh with the inbox of the selected account.
NOTE: You must have proper permissions to access different mailboxes. If you are having issues accessing a mailbox you should have access to, please reach out to the service desk for assistance.