The Easy Way - Reload BlackBerry 10 OS Using BlackBerry Link
Make sure you have the latest version of BlackBerry Link installed on your Windows PC.

  • Open BlackBerry Link and connect your device via microUSB
  • Select Settings (gear icon)
  • Select Reload under Reload Device Software
  • Follow the on-screen instructions to reload the software. When complete you can disconnect your device.
After you reload the device software we recommend setting up the device as new to prevent further issues.

Source: http://crackberry.com/how-reload-os-blackberry-z10-or-blackberry-q10