The easiest way to download ringtones to your device is to use an application which has custom ringtones available for downloading. I would like to recommend you Zedge App. You will see that it's easier to download from an application rather than creating a custom ringtone from a track which involves some difficult steps but if you choose that way, here's how to do it:
- Open iTunes and add the track you want to make a ringtone from.
- Right click the item and choose Get Info and go to Options
- Locate Start time and Stop time and mark the portion of the file you want your ringtone to be limited from. Make sure it does not overpass 30 seconds else it will not work.
- Hit OK then right click the item again but choose Convert Selection to AAC this time and you will see that the track will be added next to the original one.
- Next you will need to convert the file from M4A to M4R.
- Right click the file and use Show file in Windows Explorer. Also, please disable Hide extentions for known file types from Computer > Tools > Folder Options > Show all hidden and system files.
- Change extension from M4A into M4R and add the file again iTunes. Use Synchronize and you will be able to select the newly created ringtone from Ringtones menu in your device.