You can add 5 reminders for each event in Google Calendar. Type of reminders are Notification, Email, or Sending Text messages (SMS). Open Google Calendar on your Android device and do as follows:
1. Tap the Event you want to add reminder to
2. Under the Reminder, tap Add Reminder
3. Specify the time to be notified before the event's time (from 0 minutes to to 1 week)
4. and then specify the way to be notified (You can also change the settings for notifications under General Settings)
**** If you don't have the SMS reminder option, you need to add your mobile number to Google Calendar from a desktop browser. To add a mobile number do as follows:
1. Go to Google Calendar
2. Click the Gear Icon and go to Settings
3. Click on Mobile Setup
4. Enter your phone number, and wait for the verification code