Choose to have either an email or pop-up reminder prior to an event.  This can be chosen for all events, or one individual event. 

To receive a reminder for all events:

1) Click Preferences.

2) Go to General Settings under Calendar.

3) Next to Remind, select the time interval you would like to receive the reminder prior to the event. 

4) Indicate either Popup or Email for the type of reminder you would like to receive.

5) Click Save.

If you have reminders turned off for all events, but would like a reminder for a particular event:

1) For an event that has already been scheduled, double click on the event in your Calendar.  Click the Remind button and select the interval in which you would like to be reminded.

2) For a new event, while scheduling click the Remind button and select the interval in which you would like to be reminded.  Click Save.