When you log in a new user name for the first time, the GO config.php file can be configured to automatically assign them to a Group.
We have a group called Calendar. It assigns them to the Calendar module for access to Use (not Manage).
But - there is no way to automatically set the user up as being visible and granting access to other users to add to their calendar. It seems you must manually do that every time you add a new person.
This documentation page seems to make it look like we should be able to assign an entire Group the permissions of Read/Write and attach that group to the Calendar module. Then with a person as part of that group they would automatically get all the settings they need right off the bat. But it does not look like this on our screen! (see the bottom of the doc)