You can personalize your notification preferences to determine which course activities you wish to receive notifications for, how often you wish to be notified, and which method you prefer (e.g., email or text message).

From your Settings page, click the Notifications link in the left-hand navigation to access and edit your preferences.

In order to receive text messages for course notifications, you must go to Settings > Other Contacts > Add Contact Method to add your cell phone number.

For more info