How do I sync my music from my IPhone to ITunes on my computor?

Take a look at this link, http://support.apple.com/kb/HT1296

The iTunes content sync is one-way: Computer to Phone. For purchased iTunes content, you can transfer that from your phone to your iTunes library by right-clicking the phone in the left device pane & selecting: "Transfer Purchases". Or, you can re-download it for free directly to your iTunes library:

http://support.apple.com/kb/ht2519

If you have non-iTunes purchased music on your phone, you'll have to use third-party software to extract it from your phone.