1. purchase and install iPhone-to-computer transfer software. A number of reliable, real options are available for Mac, Windows and Linux systems.
2. Plug in your iPhone, and launch the transfer software.
3. Choose which songs you'd like to transfer from your iPhone to your computer. To pick more than one song at once, press and hold the Shift key (Windows and Mac) to select multiple songs in a consecutive row, or press and hold the Ctrl key (Windows) or Apple key (Mac) to pick specific songs individually. Click "OK," and wait for iTunes to automatically add and sort the songs in your library.