Default Utime/Charmpin G7 Rom update


I've bought an Utime G7 mobile (Android version 4.2.1, kernel version 3.4.5, build number: s33a_95045a_m11_v002_ch_20140307) from the ebay, but I forgot to tell them, that I'd like the hungarian language. How can I add this to my system? Or I've downloaded a hungarian rom from the (it contains img files, mbr, ect...), and I'd like to know, how to install it (the last time I've done something like this, I've worked with android 2.0, 3 years ago on my tablet, maybe a lot of things changed )