- flash this recovery [URL="http://xdaforums.com/optimus-g-intl/orig-development/teamwin-recovery-project-v2-8-7-0-t3160105"]TWRP[/URL]
- copy rom zip to your phone storage
- flash rom via recovery
- (only pure version) if you want root flash this [URL="https://download.chainfire.eu/696/SuperSU/UPDATE-SuperSU-v2.46.zip?retrieve_file=1"]SuperSu[/URL]
- do wipe (data, cache, dalvik-cache)
- reboot