1. After purchasing the ringtone on a computer, click the download link on the order confirmation page to download the mp3 file. You will be emailed the link to download the file as well. You can also access the link to download the file from your Order Status page. Just click the order number link for the relevant order to go to that order's detail page, then click the download link on the detail page.
2. Open iTunes. If you do not have iTunes, you can download it free from http://www.apple.com/itunes/download. Then install the program.
3. Open Preferences in the iTunes menu at the top:
4. Select the General tab:
5. Select Import Settings:
6. Click on the dropdown list after Importing Using:
7. Select AAC Encoder (it may already be the default):
8. Select OK to go back to the Preferences, then select OK again.
9. In the top menu, click File > Add File to Library.
10. Browse to the file you downloaded and click "Open" to import it.
11. After a moment, you should see the new file in your iTunes library. To the left of the search box in the top right corner, you will see three options for viewing your library. Ensure the first option is selected, which is List view.
12. Right click the clip and select Create AAC Version:
13. You should see a second version of the clip appear in iTunes.
14. Now we have to change the file format so that it will appear as a ringtone in iTunes.
15. Navigate to the folder where the new clip is stored on your computer. If you are in Windows, right-click the AAC clip and click Show in Windows Explorer. If you're on a Mac, right-click the clip and select Show In Finder.
16. Copy the clip (press Control and C for Windows, Command and C for Mac), and paste the clip in the same folder (Control and V or Command and V) so that another version appears.
17. Now, change the file extension of the new version from .m4a to .m4r. If you're on Windows XP and don't see the file extension, go to Tools -> Folder Options -> View and uncheck Hide extensions for known file types. For Vista and Windows 7: Organize -> Folder and Search Options and uncheck Hide extension for known file types.
18. In iTunes, right-click the AAC version you made previously and click "Delete" to delete that file.
19. Go back to the folder with the new ringtone file (.m4r file). Drag and drop the file into iTunes. Or import it by opening iTunes, select File, and select: Windows XP/Vista: Add File to Library, Mac: Add to Library.
20. Now we need to sync the ringtone to your iPhone. Connect the iPhone to the computer.
21. If you have iTunes set to automatically sync with your iPhone when you connect it to your computer, then the new ringtone should automatically start transferring to your iPhone when iTunes opens.
22. If you are manually managing what syncs to your iPhone when you connect it to iTunes, then click your iPhone under "Devices" in the left column in iTunes. Then in the right column, click the "Ringtones" tab. Ensure that "Sync Ringtones" is checked and the desired ringtone you want to sync is showing up under the ringtones list. Then click the "Sync" button at the bottom to begin transferring the ringtone to your iPhone.
23. While the iPhone is syncing, you will see a spinning wheel next to your iPhone under "Devices" in the left column in iTunes. When the transfer is complete, iTunes will display "iPhone sync is complete. OK to disconnect." You can then disconnect your iPhone from the computer. Your iPhone will contain the new ringtone.
24. On your iPhone, go to Settings > Sounds > Ringtone. You will see the new custom ringtone at the top of the list of available ringtones. Tap it to make the default ringtone on your iPhone.