Rather watch a video?
1. Go to the Timetable and find the activity you want to cancel.
2. When you find it, click on it. Then click on Options and select Cancel this activity.
3. Click Confirm on the popup that will appear and the activity will be cancelled.
Note: If you cancelled the wrong activity or you just want to enable it back, repeat the same process. This time, select Make activity available and then Confirm.