To import calendar data from a file previously saved using the csexport utility, use csimport. The file name extension of the import file (.ics or .xml) indicates the format in which it was saved.
For example, to import calendar data to the calendar ID (calid) email@example.com from the file jsmith.ics that was saved in iCalendar (text/calendar MIME) format:
csimport -c firstname.lastname@example.org calendar jsmith.ics
To import data into the calendar email@example.com from a file named jsmith.xml that was saved in XML (text/xml MIME) format:
csimport -c firstname.lastname@example.org calendar jsmith.xml