You can import a calendar on Apple Calendar, after exporting it as a .csv, .vcs or .ical file.
1. Select File > Import > Import.
2. Locate and select the calendar file that contains the events, and then click Import.
3. Choose a calendar to add the events to or select a calendar to add it to. Select OK.
4. If you would like to edit the name of the calendar, double click on it.