Gaming ROM Hack import tga file to igb file, on game X-men legends

[jonaand2]

Hello, i'm working in translation to spanish for game
"x-men legends" , it's a pc/ps2/gc/xbox game
only was released in english, german and french

i need add character spanish
there is a folder with name "fonts" that contain igb's file
with program
Alchemy Finalizer
extract tga's picture from file
font_xmen_big_xbox.igb

one tga file have the character

so, i edited by

for next, remplace for example á by à , etc

but i don't know how import my new tga file to igb file

any sugesstion how do it, it's only that i need, because tradution is easy
thanks so much