Set an alert for a calendar event on iCloud.com
To receive an alert for a calendar event, you need to be signed in to iCloud.com when the alert goes off. If you’re not signed in, you can still receive alerts on any device that has the iCloud Calendar feature turned on.
Set an alert for an event
In Calendar on iCloud.com, tap the event to open it (if it isn’t open already).
Do any of the following:
Set an alert: Tap the “alert” pop-up menu, then choose an option.
To remove an alert, choose None.
Set a second alert: Tap the “2nd alert” pop-up menu, then choose an option.
Set a default alert for new events
In Calendar on iCloud.com, tap the Action pop-up menu in the bottom-left corner, then choose Preferences.
In the General pane, select “Add a default alert to new events & invitations” pop-up menu, then choose an option.
If you’re not receiving alerts, make sure you’ve set the alert correctly and you’re signed in to iCloud.com.