You can use the songs from your iTunes collection to make custom ringtones for your Apple iPhone. Make certain that you use a Digital Rights Management free song as a ringtone for your phone. Songs that you may have purchased from the iTunes Store are not DRM free and be used as ringtones. You should use DRM free songs that you've imported from a music CD, or downloaded from an online music service.
Insert a music CD into your computer's CD/DVD drive. Double-click on the Apple iTunes icon on your desktop to launch the application. Click the "Import" button and then click "Yes" to import the song tracks on your CD to iTunes. When iTunes is finished importing the songs on your CD, you will hear the "Complete" sound. Remove the music CD from the CD/DVD drive.
Click on the "Music" option located on the sidebar under the "Library" section. Find a song track that you want to make into a ringtone for your Apple iPhone.
Move your mouse cursor over the song track name and right-click on it. Select the option "Create AAC Version" from the drop-down menu list. This feature will make another version of the song track in iTunes.
Play the song track and decide what part of it you want to make into a custom ringtone. Write down the numbers that represent the beginning and ending of the song that you want to use.
Click the "Options" tab on the menu bar near top of the screen. Use the numbers that you wrote down, and enter the "Start Time" and "Stop Time" of the ringtone. Press the "OK" button.
Right-click on the song track, and select "Get Info" from the drop-down menu list. Change your the ringtone file extension from ".m4a" to ".m4r" and then double-click on it. Your custom ringtone will be imported to the "Ringtones" folder in iTunes.
Use the USB cable that came with your Apple iPhone and plug it into a USB port on your computer. Go to the "Ringtones" tab on your iPhone. Tick the check box next to "Sync Ringtones" and choose the option "Selected Ringtones." Tick the check box next to the name of your new custom ringtone under the "Ringtones" section.
Click the "Settings" button on your iPhone. Select "Sounds" and then go to the "Ringtone" menu. You will see a list of ringtones on your iPhone. Click the button for your new custom ringtone to listen to it.
Disconnect your Apple iPhone's USB cable from your computer.