How to Cancel and Edit Events in iCal
Apple's iCal, which comes with Mac OS X, provides features for organizing and planning your schedule, including events with reminders. As schedules change, so do events and deleting, canceling or editing an event in iCal is just as easy as creating one. ICal events are singular, which means you will have to cancel or edit them individually. When you delete an iCal you cannot get it back.
Click the "iCal" icon in the Dock to open iCal. Alternatively, access iCal through the "Applications" folder.
Double-click the event you want to edit and then click the "Edit" button.
Click an event you want to cancel and press the "Delete" key.