1. First, open a browser on your computer, enter the letter "iTunes" in Baidu browser, and then click Search to download the application "iTunes" from official website website.

2. Double-click the icon of the application "iTunes" to open iTunes, click and select the "Files" tab in the upper left corner, and then click "Add files (folders) to the library" in the sub-column (which sub-column you choose depends on the storage of music).

3. In the pop-up file window, find the place where the music is stored, and select the music file to be added (if the music exists in the form of a file, click the file, and if the music is stored in a file, select the folder).

4. Next, connect the IPHONE to the computer with a data cable, and then ITUNE will automatically identify the connected IPHONE. Click on the "Mobile Phone" icon at the top left of the screen, and select Enter Subcolumn Settings-Music. Then continue to click Sync.

5. Finally, turn on the IPHONE, and you will find that the music has been synchronized.