The Reminders tab appears at the bottom of the ApplicantExtra screen and shows the list of events that have pending reminders set for them.

To view the list of dismissed reminders, select the Show Dismissed Reminders check box.
Click the hyperlinked event to view the event details. You can click Dismiss against an event to dismiss the reminder set.

If you do not have outlook attached to ApplicantExtra then the built in reminder system will take over (showing a reminder popup window when they are due) and a reminder window button will appear in the reminder tab.