The Ringtone  that comes in iPhone are basic but now you can change custom ringtone in your iPhone .You just need iTune software and connecting cable only.Follow these simple steps to add your own music as rintone in your  iPhone:-
Select the mp3 file that you want to use as a ringtone,we can’t use the full mp3 file as a ringtone ,for that we have to trim the file for 30 seconds only
Open the .mp3 file in iTunes. Right-click the .mp3 file and choose “Get Info“
Once the Get Info dialog comes-up navigate to the Options tab. If you are using a short .mp3 file as your source then you might not want to touch any of the settings on this tab. But if you trying to extract a portion of the .mp3 file then you wanted to key-in values for the “Start Time” and “End Time” items. Keep in mind that the total length of the ringtone can only be less than 30 seconds.
Now we are ready to convert the file to a more friendly format that .mp3. Right-click on the same file again and choose the “Convert AAC Version” option.
If you don’t see the option on your right-click menu then go to iTunes > Preferences > General Tab and click on the “Import Settings…” button. Change the “Import Using” dropdown menu to “AAC Encoder“
Once the file is converted to AAC version it generates a .m4a file. Drag the file to your Desktop (or any other location that you prefer).
Rename the .m4a file to .m4r file. If you have any questions on how to do it the safest way to do is to right-click the .m4a file and choosing the “Get Info” option.
On the dialog that comes up change the extension of the file to .m4r and confirm the rename.
Before you proceed any further you should remove the AAC version of the file that’s on your iTunes.
Now, move the .m4r file that’s on the desktop to the Ringtones folder on iTunes.
Now it’s all pretty much set for you to make use of the custom ringtone. Connect your iPhone and do a Sync.
Once successfully synced, tap on your iPhoneSettings app.

Tap on the “Sounds” option.
Then tap on the “Ringtone” option.
iPhone will now display the list of available ringtones and you should be able to see the newly added ringtone at the top of the page under the “Custom” section. Tap on the ringtone name to choose the ringtone as your default iPhone ringtone.