These are following options which can be used to manage your WP8 device from your computer
Nokia Lumia 520 Pc Software For Windows 7
How to Update My Lumia 520 to Windows Phone 8.1. Windows Phone 8.1 is now available for download for free on your Lumia 520. Simply follow the given step by step guide to update your Lumia 520 to Windows Phone 8.1. 1 Before you start. This guide will show you how to update your Lumia to the latest software version. Updates give you access to new improvements and fixes bugs on your phone.
- Connect your phone to a compatible computer with a compatible USB cable.
- On your computer, open a file manager, such as Windows Explorer or Finder, and browse to your phone.
Your phone is shown under portable devices as Windows Phone. To see the folders of your phone, double-click the name of the phone. There are separate folders for documents, music, photos, ringtones, and videos.
- Drag and drop items from your phone to the computer or from your computer to the phone.
If your computer's operating system is Windows 7 or Windows 8, you can also use the Windows Phone app. Windows 8 installs the app automatically.
With Windows 7, you can download it from http://www.windowsphone.com/.
Updating Nokia Lumia 520 Software
Nokia Lumia 520 Review
But still if you want to use Windows Phone app for desktop (Preview 3) which is still under Preview release hwoever very similar to Nokia PC Suit, you can visit below link