Connect the iPhone to a PC or Mac via USB cable and open the iTunes application.
Note: iTunes may open automatically once the iPhone is connected.
Click options icon, then click Add File to Library.
Navigate to the preferred folder and click Open.
Select the files to be added to the library and click Open.
The new files are imported to the Music Library.
Note: If iTunes does not offer direct support for a particular media format, it will prompt to convert the files to AAC. If prompted, click the preferred option.