You can always view other users’ calendars by going to your calendar and toggling the check boxes next to the names of the other users at your company. You'll see the list of names in the left column. If you don't see the name of a fellow user in the sidebar, then you don't have viewing rights to their calendar!
When you check a user’s name, their events will show on your calendar and their tasks will also show in the calendar’s task area (depending on which view you're using, this will vary).
Admins are in charge of setting up permissions for new users when they are registered, and can control whether a user can see/edit other users’ calendars. If you cannot see other users’ calendars and you need to be able to, check with the admin account at your company and they will be able to make the appropriate changes to your account as described in this article.