I see that you'd like to use a different alert sound as the notification sound for a third party application you use. I'm happy to help.
Use notifications on your iPhone, iPad, and iPod touch -- Tap Settings > Notifications and select the application. Then tap "Sounds" and select one from the list.
Customize your notifications with different alert styles so you can quickly act on emails, calendar invites, messages, and more.
To add or change an alert style for a notification, go to Settings > Notifications and select an app. Here are some alert styles that you can choose:
- Allow Notifications: Turn on to get notifications from the app you selected.
- Sounds: Have an app play a sound to alert you when you receive a notification.
- Show on Lock Screen: Turn on to see notifications from the app on your Lock screen.
- Show in History: See previous notifications from the app you select.
- Banners: Choose how you want notifications to appear when your device is unlocked. Tap Temporary to have alerts appear on the screen and then go away. Or tap Persistent to have alerts stay on the screen until you act on it.
- Show Previews: Choose what you want to see when you get a notification, like a text message.
Control the volume -- iPhone User Guide -- Since the volume for Notifications is based on the volume level your iPhone is set to, make sure that the volume is as high as you'd like.
Lock the ringer and alert volumes. Go to Settings > Sounds & Haptics (on supported models) or Settings > Sounds (other models), then turn off Change with Buttons. To limit the volume for music and videos, go to Settings > Music > Volume Limit.