Take the OPPO R9S mobile phone as an example. The setting method is as follows:

1. Open the phone, find the "Clock" item on the desktop, and click to enter.

2. After entering the clock, find the alarm clock you want to modify the ringtone and click to enter.

3. After entering, find the "Ringtone" item and click to enter.

4. After entering the ringtone settings, find the "Select from file" item and click to enter.

5. After entering, you can choose your favorite music.