Hello Bumba! You'll need the Nokia Software Updater program for your pc! When you download it, maybe it will ask you permission to install some drivers in your computer, don't be afraid and let it go! He will install the drivers automatic then you open the program update him if necessary (depends on witch version you downloaded) then plug in your beloved Lumia 520 with the usb cable of the hone and the program will warn you about an update do what he says and he will start downloading! After 30 minutes depending on the internet it will be all set! Bye amigo!