Open the Settings app
Tap Sound and vibration or Sound
Tap Phone ringtone
Select a ringtone from the list
Tap OK or Save
To use a custom ringtone, copy the audio file to the Ringtones folder
Open Settings
Tap Sound and vibration or Sound
Tap Phone ringtone
Tap Add ringtone or Custom ringtone
Select the audio file
Tap OK or Save
To set a ringtone for a specific contact, open the Contacts app
Select the contact
Tap Edit
Tap Set ringtone
Choose a ringtone
Tap Save
To set a notification sound, open Settings
Tap Sound and vibration or Sound
Tap Notification sound
Select a sound
Tap OK or Save