ToME: the Tales of Maj'Eyal

Hello, I'm korean TOME player. Pls take into account I'm not good at English. I want to make translation addons for korean players. I learn about C language programming for one semester in my university. So, I think I can make addons on my own in details. However, I don't know where to start the modification. Could anybody tell me what to do first. Actually, I don't know what files I have to decoding and how to make steam addons. I'll be very happy if someone teach me with this.