You need to make sure you meet the requirements of the application. According to the official website, the software requires:
- Windows XP, 7 or 8
- iOS 5.0 or later
- iTunes 9 or later
The first thing to do is to update the iTunes package. Make sure to download the latest package, then install it. After this procedure, browse to the official Zedge ToneSync page and download the latest version. There is also a video to guide you how to use the software.