You need the serial number and register password and call Autel Support, registration put in your name and e mail .The language change has to be authorized by Autel support and the unit  Needs to be within the free update period. Afterwards,You will probably have to do a factory reset to device  , make sure to select correct language, name ,set up register primary email address, WIFI network , and download all the system and software again in the Korean language. Warning !You will need to buy an update to get the software back if you factory reset the device and the update period is expired!