It`s pretty complicated from what I understood, since we did this in my company, but we had to implement it also with a Workpoint calendar.
If you want to get the organizational calendar on your own email, request access to it, and when you get the access, add it to your personal Outlook, and tick both of them in the Calendar tab.
To add your to the Org. one, you would need the person administrating that mailbox to add your calendar to theirs, and make it visible.
I don`t remember all the steps by heart, but it`s mostly up to your system limitations.
Do you need this for work? As in a company? Or for home usage?
If it`s for work, contact your local IS, and ask them to help you.