how do I move music from my IPHONE to my computer

If the music was purchased from the iTunes store, you can transfer it to your iTunes library by opening iTunes on your computer, authorizing it for the Apple ID(s) used to buy the music (Store>Authorize This Computer), then connect your phone to your computer and going to File>Devices>Transfer Purchases in iTunes.

The only way to transfer music from other sources to your computer is by using 3rd party software to extract it from your phone, such as Touch Copy.