Long-press wither volume button. Does a meatball icon (a "settings" icon) show up? If so, tap that. If not, go into Settings, to Sound. There should be a choice in Settings (the same screen you get from the settings icon in the volume control) with 4 volume controls. (Some manufacturers, in some versions of Android, combined Notifications and Alarms into one, but there are apps in Play to give you 4 volume controls.)