How to add ringtones to your iPhone from your computer: You'll need to have your iPhone, a USB Cable for iPhone, and have iTunes installed on your computer.
Step One - Download and import to iTunes Internet Explorer - Left click on the M4R file of your choice, and choose open. Once the M4R file is done downloading, it should automatically go into your iTunes folder under ringtones.
Firefox & Chrome - Right click on the M4R file of your choice, and choose Save Link As... Once the M4R file is done downloading to the directory that you have chosen, double click the M4R file.
Safari- Right click (Mac with one button mouse - hold the control key on the keyboard and click the left mouse button) on the M4R file of your choice, and then choose Download Linked Files As... Once the M4R file is done downloading to the directory that you have chosen, double click the M4R file.
Step Two - Display ringtones in iTunes Open iTunes on your computer. To display and preview the ringtones you have downloaded from your browser and opened, make sure that the 'Ringtones' tab in iTunes is highlighted. If you don't see a ringtones option in iTunes, go to the edit menu in iTunes and select preferences (on Macintosh, go to the iTunes menu and select preferences). Then check the ringtone check-box under sources (on Macintosh, under show) and click ok.
Step Three - Install the Ringtones on Your Phone 1) Plug in your iPhone to your computer with the USB to iPhone cable
2) Click on your iPhone under devices and then click on ringtones (see screenshot below). Make sure that 'Sync Ringtones' and 'All ringtones' are checked on.
3) Now click on the sync button in the lower right corner and let it complete a full sync. If the sync button doesn't show up, there is also a sync option under the file menu in iTunes.
On your iPhone: 4) Tap on the 'Settings' app from the home screen on your iPhone, then tap on 'Sounds' and finally tap on 'Ringtone'.

5) Under 'Custom' at the top of the screen, tap on the ringtone that you want.
