When you touch and hold a notification on the status bar, two options will appear “Alerting” / “Prioritised” and “Silent”.
a) Select “Alerting” / “Prioritised” to allow sound or vibration alerts for this app at subsequent new notifications.
b) Select “Silent” to mute all notifications from this app
You can go to “Settings”->“Apps” ->“VIEW ALL ×× APPS”->select the app you want to set->“App notifications” to take advantage of additional set up options.