How to set a music file as a ringtone on Galaxy phone?

1 From the home screen, choose Apps or swipe up to access your apps

2 Select Settings

3 Tap Sounds and Vibration / Sounds and Notification / Sounds

4 Select Ringtone

5 Select between Sim 1 / Sim 2

6 The available ringtones on your device will show up, to add your own ringtone tap on plus (+) or Add Ringtone 
( You may have to scroll down to locate )

7 If prompted, tap the Sound Picker and tap Allow

8 Choose the music file and you are set   

To change background color of Ambient Mode :

1 Move focus to Brush icon in the browser screen, and then press the Select button. You can change the background colour or pattern. Move the focus to a colour or pattern you want, and then press the Select button.

1 Tap Contacts or Phone

2 Tap the desired Contact

3 Tap Details > Edit

4 Select Videw More > Ringtone > Add or Add Ringtone > Soundpicker