You can change the sound and notification settings on your device by going to [SETTINGS ICON] Settings > Device > 
Sound & Notifications
Notifications alert you to the arrival of new messages, calendar events, and alarms, as well as ongoing events, such as downloads:
Interruptions
Prioritise sound notifications so they don’t interrupt you. Touch the settings to turn phone calls and message interruptions on or off. If you turn Message Notifications on, touch Calls/Messages from to specify from whom you accept notifications (Anyone, Starred Contacts or Contacts Only). In Downtime, select which days and times you allow for sound notifications.
When device is locked
Manage whether notifications can be seen when your phone is locked, and whether sensitive content in a notification can be seen. Sensitive content includes things like the title of a song you downloaded, who sent you an email, or the details of a calendar event.
App notifications
Modify the notification settings individually for apps such as Gmail. The setting under ‘When Device is Locked’ will always take precedence over the individual app.
Notification Access
See which apps can access your notifications
When a notification arrives, it’s icon appears at the top of the screen. Icons for pending notifications appear on the left, and system icons showing things like the Wi-Fi signal, mobile carrier signal, or battery strength are on the right:
TIP: Wi-Fi and Mobile Signal Strength are indicated at the top of the screen by white bars, to see whether the selected Wi-Fi network has a full internet connection, open quick settings by swiping down with two fingers from the top of the screen.
In quick settings only, white bars in the Wi-Fi or mobile signal indicators indicate the signal strength or a normal internet connection.
Certain notifications can be expanded to show more information, such as email previews or calendar events.
The one at the top is always expanded when possible. To expand a notification, position one finger inside it and swipe down slowly.
To open the related app, touch the notification icon on the left. Some notifications also allow you to take specific actions by touching icons within the notification. For example Calendar notifications allow you to Snooze (remind you later) or send email to other guests.
When you’re finished with a notification, swipe it away. To dismiss all notifications, touch 
Dismiss at the very bottom of the notifications list.