1. Go to Notification menu , just next to Spotlight search icon on the top right
2. Now at the bottom right of the notification screen you will see a Setting icon, click on it
3. Notification Setting Dialog will pop up
4. Click on the image next to Turn on Do Not Disturb Notification Center
5. Now the Notification Center slides out, you would now see DND button at the top
6. Turn it ON/OFF to enable/disable Notifications.