Just connect your device to computer via USB cable and then transfer audio directly.
Or you can user Android Assistant program,which can connect your device to computer and enables you to transfer data between them.What's more,before transferring,you can preview the details.https://www.mobikin.com/assistant-for-android/

To Transfer Audio Files from a PC and Set Custom Ringtones & Notifications on your Samsung Galax S, try a third-party program like Coolmuster Android Assistant. With its help, we can easily import data like audio files from a computer to it.

Transfer Audio Files from a PC:

1. Connect the Android phone to the PC via USB
2. Enable “Media device” / “File Transfer” at the prompt or from the Notification area
3. Launch the File Explorer on the computer and navigate to the audio files on the PC
4. Copy and paste the desired audio files to the phone storage, preferably in the “Ringtones” and “Notifications” folders
5. Once the transfer completes, you can safely disconnect the device from the USB port

Change the General Ringtone:

1. Open “Settings”
2. Go to “Sound and vibration”
3. Tap “Ringtone” and select the desired ringtone
4. Press “Back” to confirm

Change the Ringtone of a Specific Contact:

1. Go to “Settings”
2. Access “Sound and vibration”
3. Tap “Ringtone”
4. Select the ringtone you want to use and tap “back”

Change the Ringtone of a Specific Contact:

1. Open “Contacts”
2. Tap the desired contacts and go to “Details”
3. Tap “Edit” > “More” > “Ringtone”
4. Tap “Allow storage permission” and set to “Allow”
5. Select the desired ringtone and tap “OK”

Change Incoming Email Notification Settings:

1. Launch “Email” and tap “Menu”
2. Go to “Settings” > “Manage accounts”
3. Select your email address and go to “Notification settings”
4. Tap “Email notifications” and tick or clear the desired check boxes
5. Optionally, you can also enable or disable “notification sound” and “Vibrate”

Change Emergency Alert Settings:

1. Launch “Messages”
2. Tap “Menu”
3. Go to “Settings” > “Emergency alert settings”
4. Tap “Emergency alerts”
5. Turn ON or OFF “Imminent extreme alerts”, “Imminent severe alerts” and “AMBER alerts”