To manage the notification reminder of the activities, navigate to the ‘Notifications’ You will get the two options: Notifications for the Calendar page and Desktop Notifications.
Click on the On option to enable.
Notifications: You will get the notification reminder about upcoming activity when you are on the Calendar page.
Desktop Notifications: You will get the notification reminder about upcoming activity as Desktop Notifications
Minutes: Set the minutes to be notified just before starting the activity.