It's easy to share meetings and events privately within your organization.  Organization members may login with their email/username and password.  You can also embed the calendar into an intranet site.
 

 Create Private Categories:

Use categories to group events into separate calendars and set private viewing permissions. For example, you might create a private "administration" category. You may also create a category for each department and only allow department members to view that category.
To add a private category:

Click the Admin Menu button > under Calendar Settings > Categories > Add > Enter a title >
Set "Viewing Permissions" as B. Private - viewable only by logged-in users or  C. Selected Private - viewable only by selected logged in users > Save
 

 Create Users
 

Create users so they may login to view (and, optionally edit)  private categories.

Admin Menu > under Calendar Settings > Users & Subscribers > [Invite User]  >
Enter user's email. Allow a user to create their own password or you can create own for them >

If you like, give the user set editing permission > [Save]
 

 Create a link that automatically logs into the calendar:

You can embed a logged-in link into a password protected website or intranet site so that organization members don't have to login to the calendar after logging into your intranet site.

https://www.calendarwiz.com/calendars/calendar.php?crd=yourcalendaridentifier&psw=userpassword&scr=username&nolog=1

- Replace "yourcalendaridentifier" with your unique calendar identifier name. 
- Replace "username" with either the user's email address or username.
- Replace "userpassword" with the user's password.

Important Note:  Be sure that you've set appropriate viewing and editing privileges for the username and userpassword. 
To hide the "logout" button insert the &nolog=1 parameter.  You may embed this link inside an iframe on a password protected site.