iPhone comes with ringtones that sound for incoming calls, Clock alarms, and the Clock timer. You can also purchase ringtones from songs in the iTunes Store. 

Set the default ringtone. Go to Settings > Sound > Ringtone.

Assign different ringtones for the special people in your life. Go to Contacts, choose a contact, tap edit, then tap Ringtone.

Turn the ringer on or off. Flip the switch on the side of iPhone.

Important: Clock alarms still sound when the Ring/Silent switch is set to silent.

Turn vibrate on or off. Go to Settings > Sounds.