how to install 4.1 from 4.0 jiayu g3

hi complete android newb with my first android phone here, sorry if this is in the wrong forum but there are so many sections and this seemed the most appropriate

i bought a Jiayu G3 on icecream sandwhich and id like to install the 4.1 upgrade from this website about halfway down the page:

Official Jiayu-ROM (pre-release, modified) / 01.16.2013 / 4.1.2
Pre-rooted. Notification LED works. Stable and fast to run and also has an improvement in the camera. Problem with the second SIM for video telephony. Download is under the source (run only via update function of existing original ROM!) As a version for recovery flash and ready as a variation for the flash tool.
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clicking the download button has a few things to download but i have no idea how to install it etc, the most experience i have with installing hybrids and updating the os is from blackberry which is completely different (from what i can see)

the only update tutorials i can find are for the main androids with different download files so im not sure what to do

if anyone could help me with this step by step id really apppreciate it, also how would i back up my information so i can restore after the update?