The Apple iPhone comes with a set of built-in ringtones. However, some may find this selection of ringtones limiting. Fortunately, the Apple iTunes store allows you to purchase ringtones. A simple sync up with your computer will automatically transfer any purchases made on your computer with your iPhone. Transferring ringtones from one iPhone to another is not difficult given you have the most recent versions of the iPhone and iTunes software.
Open iTunes on your iPhone by pressing the "iTunes" icon.
Press "Ringtones." It is the icon that looks like a bell.
Browse the selection of ringtones. When you find one you like, select it, enter your password and wait for the ringtone to finish downloading. It should now automatically be a selectable ringtone for incoming calls.
Connect the iPhone to the computer with the USB cable that came with the iPhone. iTunes on your computer should automatically open. iTunes will automatically sync with your iPhone, importing all new content. This includes the ringtone.
Unplug the USB end from your computer and the non-USB end from your iPhone once syncing is completed.
Connect the other iPhone to the computer using the USB cable.
Choose to sync the iPhone with the computer once prompted.
Wait for the sync to be completed to unplug the cord from both the computer and the iPhone. The ringtone should have transferred successfully to the other iPhone.
When syncing the second iPhone to the computer, you risk losing saved content on the iPhone. The process may replace your pre-existing content with the content stored on the computer. Be sure to back up your iPhone's content on another computer or an external hard drive.