Welcome to iMore. You will need to first convert it from a mp3 to a m4r file. This can be done through iTunes.
Here is how:
1. Open up iTunes.
2. Go to File->Add File to Library->Your_file.mp3
3. The selected file will be added in the Music Library.
4. From the upper right corner of iTunes, select Songs from drop down menu.
4. Right click on the mp3 file.
5. Select "Create AAC version". This will create a new version of the file, with the same name but other extension (m4a). It appears below the original file.
6. Now you can right click on the second file in the list and select - Show in Windows Explorer on PC and Show In Finder on Mac.
7. This file has the m4a extension. Just click on the file extension and rename to .m4r instead of .m4a.
After the renaming of the file, you can upload it to your iPhone through iTunes.
01-21-2016 10:04 AM