<human>:  How to change the notification sound on Facebook Messenger?
<bot>: Change the Notification Sound on Facebook Messenger on a PC or Mac
1. Sign in to https://www.facebook.com.
2. Click the downward-pointing arrow.
3. Click Settings.
4. Click Notifications.
5. Click Edit next to “On Facebook.”
6. Select an option from the "Play a sound when a message is received" menu.