You can use your iPhone to buy and download 256 kbps ringtones from the iTunes Store. An iTunes Store account and a 3G or Wi-Fi connection are required.
To browse for ringtones on your iPhone, first tap the iTunes icon on the home screen, and then tap Ringtones at the bottom of the screen (or look for Ringtones in More if you do not see it in your menu bar). Tap any ringtone’s name to hear a full-length preview. When you’re ready to buy a ringtone, tap the price, and then tap Buy Now. Sign in to your account when prompted, and then tap OK. For more information, see Purchasing Ringtones.
At the time you purchase a ringtone, you can set it as your default ringtone or assign it to a contact. If you want to decide how to use your ringtone at a later time, see Setting Ringtones.