How to easy Update Sony Xperia Arc S to CM 10.1 Android 4.2.1 Jelly Bean

Android 4.1 Jelly Bean is still far-off from reaching Sony Xperia Arc and Arc S but with the help of CyanogenMod 10.1 you will get Android 4.2.1 Jelly Bean goodness right on your phone. If you want to get Google Now and Venture Butter, improve now with CM10.1!
Warning: This is a custom ROM and developers are not liable for any damages which may occur on your device. Read and follow the instructions carefully to avoid any errors. Do this at your own risk.

Requirements:

• This custom ROM is only valid for Sony Xperia Arc series and flashing this to other devices can cause terrible results.
• Make a backup of all personal information, settings and data files before flashing the ROM.
• Battery level must be at least 80 per cent to avoid power interruption.
• Your Xperia Arc or Arc S must be rooted.
• Enable the USB Debugging mode; Settings > Application > Development > USB Debugging.
• Download the CM10.1 custom ROM and the Google Apps package for Xperia Arc.

Flashing Instructions
1.      Connect your Xperia Arc to the computer using a USB cable.
2.      Copy both the CM10.1 custom ROM and the Google Apps package on your device.
3.      Disconnect it from the computer and turn off the device.
4.      Press both Volume Down and Power keys to reboot the phone into Recovery mode.
5.      Inside the Recovery mode, perform a nAndroid backup of the current ROM by selecting "backup and restore."
6.      Go back then select "wipe data/factory reset" and "wipe cache partition."
7.      After the complete wiping, select "install zip from SD card > choose zip from SD card." Choose the CM10.1 custom ROM you have copied earlier and confirm installation. Do the same with the Google Apps package.
8.      Go back in the main menu and select "reboot system now." The device will reboot and usually takes 5 minutes to complete the first run.
All done! Your Sony Xperia Arc or Arc S is now running Android 4.2.1 Jelly Bean with CyanogenMod 10.1. To confirm the current firmware, go to "Settings > About Phone > Firmware Option."