Access the Sound Settings: On your Android device, go to Settings, then Sound, and find the section for Ringtones or Sounds.
Choose a Default Ringtone: If you wish to use one of the pre-installed ringtones, simply select it from the list provided.
Using a Song as a Ringtone: To set a song as your ringtone, copy the audio file to your device's internal storage or SD card. Then, navigate to the Ringtones section in Sound Settings, tap on the "+" or "Add" button, and browse for the desired song file. Select it, save your changes, and you're done!