Install Android 4.2 on the Samsung Galaxy S3 (All Variants)

Prerequisites:

• Rooted Samsung Galaxy S3 (how to)
• Unlocked Bootloader (how to)

Downloads:

• Android 4.2 Download (please choose your carrier)
  • Verizon | T-Mobile | AT&T | Sprint | International | US Cellular | Metro PCS
• GAPPS (Google Apps) Download

Procedure

• Place the two files on your SD Card
  • *Download the files directly on the device to place them in your internal storage
• Download Rom Manager
  • *This is a free root required application that allows you to boot into recovery, manage roms, and manage backups.
• Reboot into Recovery
  • *Using Rom Manager, navigate to “Reboot Recovery”
• Backup your current rom
  • *Using the volume rocker as up/down, navigate to “backup”, and select with the power button.
• Clear Data and Cache
  • *Using your volume rocker as up/down, navigate to “Wipe Data/ Factory Reset”, and select with the power button. Then navigate to “Wipe Cache partition”, and select with the power button.
• Install the Android 4.2 rom
  • *Using your volume rocker as up/down, navigate to “Install Zip from Internal”, then navigate to the “download” folder, and select the Cyanogenmod 10.1 .zip file.
• Install the GAPPS
  • *Using your volume rocker as up/down, navigate to “Install Zip from Internal”, then navigate to the “download” folder, and select the GAPPS .zip file
• Reboot and Enjoy
  • *You’re done!

Please remember that rooting and flashing custom roms to your device can be very, very dangerous. AndroidGuys.com and myself are not responsible for any problems that may occur during this process. For an added tutorial, please view the attached video for a visual step-by-step tutorial.

 

Source

http://www.androidguys.com/2013/01/23/tutorial-run-android-4-2-on-the-samsung-galaxy-s3/