Inside of "Calendar Permissions", you can add and remove the users that you need to share the calendar with.  Note: You need to set their permission level based on what you want them to do.  Some common ones:

Free/Busy time - Only shows whether you're free or busy, can't see event details

Reviewer - Can't edit anything but can see all events

Owner - Can manage everything

After that hit OK and it will be shared.

Then find the user's name and make sure Folder Type is set to Calendar and hit OK.