I downloaded a custom notification and set it in my settings, but it is too annoying so I want to change it back to the default, but can't find it. I know how to change it, just can't find it.
Welcome to Android Central! Are you trying to change the system-wide notification to something else, or an app-specific notification?
If it's system-wide, go to Settings>Sound>Notifications, and select a new tone from there. If it's app-specific, then open that app, tap Menu, then Settings, then look for notification options.